SEARCH-666: Use quality names rather than numeric IDs

[reosarevok]

Fix SEARCH-666

Problem

Our documentation claims that you can search release quality using the words "high", "normal" and "low". That's not the case though - for some reason, release indexing was implemented by just indexing the quality as a number straight from the DB.

This causes several problems:

• It's inconsistent with lookup and browse calls, which return quality as text (searches do not return quality at all, which seems suboptimal, added SEARCH-698 for that).
• Something breaks when searching for low quality releases by passing 0 (maybe it's being evaluated as falsy).
• It is undocumented and goes against user expectation since these numeric IDs are not exposed anywhere on the website AFAICT
• Normal is split between 1 and -1 - we do this at the database level to know which releases have been set to normal manually (1) vs the ones that have the default quality level (-1) but we do not differentiate them in user-facing locations elsewhere.

Solution

Add a transform function quality_to_string that maps 0 to low, 2 to high, and other options (that is, -1 and 1) to normal. This matches what we do elsewhere in the API, matches what was listed in our documentation, and removes the split between -1 (default) and 1 (normal) which we don't generally expose to data users.

Testing

Updated the testing data so that not all the qualities are -1, otherwise just letting the existing test do its thing.

Actions

• Revert https://wiki.musicbrainz.org/index.php?title=MusicBrainz_API/Search/ReleaseSearch&diff=76136&oldid=75135