Ytdl-sub

[BACKEND] `elif` scripting function (876)

As titled

[BACKEND] More url variables in helper preset (874)

Have `url` variables go up to 100

[BACKEND] Info log for `filter_include` and `filter_exclude` plugins (873)

Adds more verbose logging when entries get filtered using the `filter_include` and `filter_exclude` plugins

[BACKEND] Optimize memory usage (872)

Reduce memory usage significantly when pulling large channels all at once by
- Not loading entry script until it is being processed
- Deleting the entry memory once fully processed
- Disable yt-dlp from keeping entry info in memory since ytdl-sub reads it from file

[BACKEND] Set `max_downloads` to `keep_max_files` if present (871)

Implements: https://github.com/jmbannon/ytdl-sub/issues/829

Optimization to not scrape more than what you will keep

[BUGFIX] Properly handle UIDs that have misbehaving chars that get sanitized (870)

Should hopefuly fix both:
- https://github.com/jmbannon/ytdl-sub/issues/843
- https://github.com/jmbannon/ytdl-sub/issues/867

Various sites have unique IDs with characters that get sanitized (i.e. `/`, `:`). `ytdl-sub` was not using sanitized UIDs when looking for files, and would throw an error saying download was missing. This should resolve that issue.