Repository: yt-dlp
Issue: Add lowercase & uppercase flags for string formatting / output template
Labels: enhancement

Original title:
## %(extractor)s is case-sensitive, but --download-archive saves extractor in lower_case. It would be nice to reconcile both.

### DO NOT REMOVE OR SKIP THE ISSUE TEMPLATE

- [X] I understand that I will be **blocked** if I *intentionally* remove or skip any mandatory\* field

### Checklist

- [X] I'm reporting a bug unrelated to a specific site
- [X] I've verified that I'm running yt-dlp version **2023.07.06** ([update instructions](https://github.com/yt-dlp/yt-dlp#update)) or later (specify commit)
- [X] I've checked that all provided URLs are playable in a browser with the same IP and same login details
- [X] I've checked that all URLs and arguments with special characters are [properly quoted or escaped](https://github.com/yt-dlp/yt-dlp/wiki/FAQ#video-url-contains-an-ampersand--and-im-getting-some-strange-output-1-2839-or-v-is-not-recognized-as-an-internal-or-external-command)
- [X] I've searched [known issues](https://github.com/yt-dlp/yt-dlp/issues/3766) and the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues **including closed ones**. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)

### Provide a description that is worded well enough to be understood

The option `--download-archive archive.txt` saves all extractors in lower case.
But if I use `--print-to-file after_move:"%(extractor)s %(id)s" archive.txt` it would save as extractor with the same case it's listed in `yt-dlp --list-extractors`, and it's often capitalized.

Concrete example:
`yt-dlp --download-archive archive.txt https://www.yahoo.com/video/intheknow/mesmerizing-giant-snow-blower-makes-165355932.html`
would produce `archive.txt` with content `yahoo 90efff2b-12ad-39bb-a351-1c890567262c
`

`yt-dlp --print-to-file after_move:"%(extractor)s %(id)s" archive.txt https://www.yahoo.com/video/intheknow/mesmerizing-giant-snow-blower-makes-165355932.html`
would save it as `Yahoo 90efff2b-12ad-39bb-a351-1c890567262c`

The reason it's a problem - after a video got downloaded with `--print-to-file after_move:"%(extractor)s %(id)s" archive.txt` and the same video gets downloaded again, but this time with `--download-archive archive.txt`, the program should be skip it, but it would not be because `Yahoo` and `yahoo` in `archive.txt` get treated as different extractors.

### Provide verbose output that clearly demonstrates the problem

- [X] Run **your** yt-dlp command with **-vU** flag added (`yt-dlp -vU <your command line>`)
- [ ] If using API, add `'verbose': True` to `YoutubeDL` params instead
- [X] Copy the WHOLE output (starting with `[debug] Command-line config`) and insert it below

### Complete Verbose Output

```shell
[debug] Command-line config: ['-vU']
[debug] User config "/home/lom/.config/yt-dlp/config": []
[debug] Encodings: locale UTF-8, fs utf-8, pref UTF-8, out utf-8, error utf-8, screen utf-8
[debug] yt-dlp version stable@2023.07.06 [b532a3481]
[debug] Python 3.11.3 (CPython x86_64 64bit) - Linux-6.4.12-arch1-1-x86_64-with-glibc2.38 (OpenSSL 3.1.2 1 Aug 2023, glibc 2.38)
[debug] exe versions: ffmpeg 6.0 (setts), ffprobe 6.0, phantomjs broken, rtmpdump 2.4
[debug] Optional libraries: Cryptodome-3.12.0, brotlicffi-1.0.9.2, certifi-2023.07.22, mutagen-1.46.0, secretstorage-3.3.3, sqlite3-2.6.0, websockets-10.4
[debug] Proxy map: {}
[debug] Loaded 1855 extractors
[debug] Fetching release info: https://api.github.com/repos/yt-dlp/yt-dlp/releases/latest
Available version: stable@2023.07.06, Current version: stable@2023.07.06
yt-dlp is up to date (stable@2023.07.06)
```