Add vocals censorship chart feature (core)

[Supersonicboss1]

As described here: https://docs.google.com/document/d/1L5yDejAOpbSnDvicgh6Id0aIeMewORVBQRStErAnogw/edit?usp=sharing

This encompasses three parts, each of which are technically independent from each other, but all of which depend on the "Censor Mature Content" setting being enabled in YARG:

1. Stems - Depends on [stem]_clean or [stem]_explicit files being present. If censor mature content is disabled, loads the normal vocal stem, and if present, the _explicit file. If the setting is enabled, attempts to load _clean, then if it does not find that for a particular stem, loads the normal variant.
2. Content Rating - If a song is rated as "Mature" or "Sensitive Content", and clean_vocals = 1 is found in the ini, drop the rating to "Supervision Required".
3. Chart - If the [CENSORSHIP_MARKERS] text event is found in that vocals part, anywhere where MIDI note 104 is covering a vocal note, remove the note, and replace the entire word with a dash. The state of this setting is also stored in replays, to ensure correct playback.

While I am relatively happy with the stem and content rating implementations, I am unsure about the chart stuff. The way I have it implemented here is as a public post-processing step in SongChart, which applies the transformation. Not sure if this is better, or if passing it further up the chain to MoonSongLoader (or handling it in GameManager) is a better idea. Furthermore, because of the way this works, it requires looking at vocal notes in MoonSongLoader's lyric parsing which doesn't deal with flags at all, making it a bit less clean.

Also, sorry about the random whitespace changes, I have no idea how to make Rider stop doing that.

Depends on YARC-Official/YARG#1529

[wyrdough]

I have not done a full review, but a quick read-through of the diff did not show any obvious glaring architectural issues, so I don't think any massive redesign is going to be required before merging this.

Thanks for handling this, I know there are some team members who are quite interested.

[wyrdough]

This is what I can see from looking at the diff alone. Feel free to push back, because I'm definitely missing context.

[wyrdough]

Shouldn't this have changed to public SongRating SongRating => GetSongRating(); instead of being deleted outright?

[Supersonicboss1]

I wasn't sure if I should enforce an explicit contract with any code that gets SongRating - essentially, should they be required to consider explicitly whether to return that with censorship enabled or not?