type hints for pytorch models
Author: robotjellyzone
Pull request: yes

# What does this PR do?
Fixes #16059  :

Added type hints for pytorch models - `canine`, `convbert`, `convnext`,  `encoder_decoder`, `gpt2`, `gptj`, `megatron_bert`, `mobilebert`, `perceiver`, `retribert`, `swin`, `transfo_xl` & `van`. 

For the code quality,  I ran **`make fixup`** and reformatted the codes & also resolved consistency problems across other models [which were - `decision_transformer`, `glpn`, `maskformer`, & `segformer`]

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## Before submitting
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## Who can review?
@Rocketknight1 

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Models:

- albert, bert, xlm: @LysandreJik
- blenderbot, bart, marian, pegasus, encoderdecoder,  t5: @patrickvonplaten, @patil-suraj
- longformer, reformer, transfoxl, xlnet: @patrickvonplaten
- fsmt: @stas00
- funnel: @sgugger
- gpt2: @patrickvonplaten, @LysandreJik
- rag: @patrickvonplaten, @lhoestq
- tensorflow: @LysandreJik

Library:

- benchmarks: @patrickvonplaten
- deepspeed: @stas00
- ray/raytune: @richardliaw, @amogkam
- text generation: @patrickvonplaten
- tokenizers: @n1t0, @LysandreJik
- trainer: @sgugger
- pipelines: @LysandreJik

Documentation: @sgugger

HF projects:

- datasets: [different repo](https://github.com/huggingface/datasets)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Examples:

- maintained examples (not research project or legacy): @sgugger, @patil-suraj
- research_projects/bert-loses-patience: @JetRunner
- research_projects/distillation: @VictorSanh

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Comments:
_The documentation is not available anymore as the PR was closed or merged._

@Rocketknight1  I have added the changes suggested by you & all checks are passing!

Looks great, thanks for the PR!