Using https://github.com/asottile/pyupgrade
1. `__future__` imports and `coding: utf-8` were removed
2. Files were rewritten with `pyupgrade --py36-plus --keep-percent-format`
3. f-strings were cherry-picked from `pyupgrade --py36-plus`
Extractors are left untouched (except removing header) to avoid unnecessary merge conflicts
PR: https://github.com/ytdl-org/youtube-dl/pull/29688
Closes: #617, https://github.com/ytdl-org/youtube-dl/issues/29665
* Livestreams are untested
* If using ffmpeg as downloader, v4.3+ is needed since `-http_seekable` option is necessary
* Instead of making a seperate key for each arg that needs to be passed to ffmpeg, I made `_ffmpeg_args`
* This deprecates `_seekable`, but the option is kept for compatibility
Authored by: nchilada, pukkandan
* All modules and binary names are changed
* All documentation references changed
* yt-dlp no longer loads youtube-dlc config files
* All URLs changed to point to organization account
Co-authored-by: Pccode66
Co-authored-by: pukkandan
