processor tests: use tiny Hub repos to reduce CI memory
Author: ydshieh
Pull request: yes

<!-- ci-dashboard-badge:start -->
[![CI](https://transformers-ci.lor-e.huggingface.cool/badge/pr?pr=47115)](https://transformers-ci.lor-e.huggingface.cool/d/pytest-observability-by-pr/pytest-observability-branch?var-pr=47115)
<!-- ci-dashboard-badge:end -->

(merged as it's just to use tiny processor on the hub)

## Summary

A follow-up PR of #47104

Processor tests currently load full pretrained tokenizers (up to 256k vocab, ~300 MB each) at `setUpClass` time, causing excessive RSS growth per test run. This PR introduces tiny Hub repos (`hf-internal-testing/tiny-processor-*`) with trimmed tokenizers (~500 tokens) for 38 processor test files, plus a tiny `DacModel` for the Dia test.

**Changes:**
- `tests/test_processing_common.py`: added `tiny_model_id` class attribute. When set, `tmpdirname` holds the tiny processor (used by all tests); `full_tmpdirname` holds the full processor only when `model_id` is also set (used by the few tests that need hardcoded token IDs). If `model_id = None`, `full_tmpdirname` is skipped entirely.
- 38 processor test files: set `tiny_model_id = "hf-internal-testing/tiny-processor-<model>"`.
- `tests/models/dia/test_processing_dia.py`: use `hf-internal-testing/tiny-dac-44khz` (0.54 MB vs ~95 MB).
- `tests/models/seamless_m4t/test_processing_seamless_m4t.py`: use `hf-internal-testing/tiny-processor-seamless_m4t`.

## Memory impact (measured on Linux CI, 39 test files)

| | Total delta MB | Duration | Entries ≥ 100 MB |
|---|---|---|---|
| **Before** | 18,291 MB | 2,793s (46.5 min) | 36 |
| **After** | 7,482 MB | 326s (5.4 min) | 24 |
| **Reduction** | **−59%** | **−88% (8.6×)** | **−33%** |

**Notable individual fixes:**
- `llava`: 428 → 33 MB
- `fuyu`: 347 → 50 MB
- `altclip`: 254 → 6 MB
- `trocr`: 251 → 11 MB
- `colqwen2`: 111 → 5 MB
- `idefics3`: 102 → 4 MB
- `gemma3n`: 91 → 4 MB
- `lighton_ocr`: 37 → 4 MB

### Before — 38 models, 18,291 MB total delta, 46.5 min

```
   Max dMB   Total dMB   >=10MB   Wall Time  Model
----------  ----------  -------  ----------  --------------------
  +   428.8       490.8        3       27.2s  llava
  +   424.4       948.9       11      162.5s  minicpmv4_6
  +   402.3       988.8       12       71.2s  qwen2_5_omni
  +   347.7       860.2        4      103.3s  fuyu
  +   254.3       638.8        7      111.1s  altclip
  +   251.5       637.4        6      112.1s  trocr
  +   213.7       521.5        6      130.2s  glm4v
  +   210.3       545.6        7       63.5s  qwen3_vl
  +   172.9       461.3        7      132.8s  glm46v
  +   166.9       816.2       14       64.1s  qwen2_vl
  +   156.5       500.8        7       29.5s  llava_next_video
  +   155.2       442.3        9       50.2s  kosmos2_5
  +   128.2       655.8       12       63.0s  qwen2_5_vl
  +   126.6       264.8        2       19.3s  idefics2
  +   126.3       695.5       12       67.2s  internvl
  +   124.6       432.8        6       95.6s  ernie4_5_vl_moe
  +   124.1       428.2       10       66.6s  video_llama_3
  +   111.2       347.7       11       44.3s  colqwen2
  +   107.9       382.0        6       74.1s  qwen3_omni_moe
  +   102.3       600.8       13      106.1s  idefics3
  +    98.4       764.4       15       38.4s  smolvlm
  +    92.9       603.3       12       92.3s  mllama
  +    91.2       586.6       12      170.0s  gemma3n
  +    89.6       563.8       21       14.1s  owlv2
  +    84.8       298.4        6       60.2s  csm
  +    70.2       514.7       12       48.6s  qianfan_ocr
  +    69.1       327.5        8       43.0s  qwen2_audio
  +    61.1       547.8       13       95.0s  pixtral
  +    60.2       265.9        7       46.6s  janus
  +    56.2       246.1        5       25.4s  donut
  +    50.6       388.5       12      100.1s  mistral3
  +    43.2       402.1       15       69.4s  aria
  +    37.8       308.5       11      148.8s  lighton_ocr
  +    28.8       165.5        3      124.7s  glm_image
  +    26.2       431.1       25       14.1s  clip
  +    24.7       165.9        3      104.8s  aya_vision
  +    12.6        19.5        1        1.9s  parakeet
  +    10.0        30.8        1        1.6s  grounding_dino
```

### After — 38 models, 7,482 MB total delta, 5.4 min

```
   Max dMB   Total dMB   >=10MB   Wall Time  Model
----------  ----------  -------  ----------  --------------------
  +   376.8       548.1        2        6.1s  qwen3_vl
  +   327.6       513.2        3       16.9s  qwen2_5_omni
  +   323.6       650.2        4        8.4s  minicpmv4_6
  +   279.7       455.0        3        6.6s  glm4v
  +   245.6       379.4        2        8.2s  qwen2_vl
  +   237.4       394.9        2       18.8s  ernie4_5_vl_moe
  +   235.2       389.4        2        8.2s  internvl
  +   198.5       812.4       13       15.7s  smolvlm
  +   195.3       501.4        7        9.0s  llava_next_video
  +   170.9       304.0        2        8.2s  qwen2_5_vl
  +   147.5       235.9        3       17.4s  kosmos2_5
  +   145.3       360.3        4        3.8s  idefics2
  +   126.2       256.8        2        9.4s  glm46v
  +   119.4       154.2        2       10.4s  video_llama_3
  +    89.2       288.4        5       15.0s  qwen3_omni_moe
  +    61.2       171.8        3       13.9s  qwen2_audio
  +    50.7        95.5        2       15.6s  mistral3
  +    50.6        85.7        2       14.0s  fuyu
  +    46.9       239.9       10        2.2s  owlv2
  +    42.3        67.8        2        5.8s  csm
  +    41.7       122.6        4        5.3s  qianfan_ocr
  +    33.5        76.6        2        5.0s  llava
  +    30.3        67.1        2       11.9s  pixtral
  +    25.1        43.1        1        8.1s  mllama
  +    21.9        53.4        3        5.8s  aria
  +    15.1        47.6        2        2.2s  clip
  +    12.5        14.7        1        2.2s  parakeet
  +    11.4        25.7        1        1.8s  trocr
  +     7.3        11.1        0        9.8s  donut
  +     7.2        10.0        0        9.3s  glm_image
  +     6.9        27.0        0        2.1s  grounding_dino
  +     6.1         9.5        0        5.1s  altclip
  +     5.4         9.5        0        2.8s  colqwen2
  +     5.1        16.4        0        5.3s  aya_vision
  +     4.6        12.1        0        5.6s  janus
  +     4.6        12.8        0        4.7s  lighton_ocr
  +     4.0         9.2        0       13.7s  gemma3n
  +     4.0         8.9        0       11.2s  idefics3
```

Remaining high-memory entries (24) are all video/audio frame loading (`test_apply_chat_template_video_frame_sampling`) — a separate issue unrelated to tokenizer size.

Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_47115). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

**[For maintainers]** Suggested jobs to run (before merge)

run-slow: altclip, aria, aya_vision, clip, colqwen2, csm, dia, donut, ernie4_5_vl_moe, gemma3n, glm46v, glm4v, glm_image, grounding_dino, idefics2, idefics3

<!-- ci-dashboard-recap:start -->

---

### CI recap

**Dashboard:** [View test results in Grafana](https://transformers-ci.lor-e.huggingface.cool/d/pytest-observability-by-pr/pytest-observability-branch?var-pr=47115)
**Latest run:** [28853489501:1](https://github.com/huggingface/transformers/actions/runs/28853489501)
**Result:** `failure` | **Jobs:** 15 | **Tests:** 171,273 | **Failures:** 6 | **Duration:** 20h 26m

<!-- ci-dashboard-recap:end -->