WIP Feature: Character role based filters (Main, Supporting and Background)

[mmshivesh]

Draft Pull request adding support for role based filtering of Characters included in the metadata:

• Introduces a selection group with option to choose between Main, Supporting and Background Character filters. Can be grouped together with the filters included in Feature: Decouples VA filter from the title language, and moves to the new Anilist StaffLanguage API key #65 to dial in exactly the Voice actors to include in the metadata (closes Option to limit the number of cast+crew entries #43)

• UI Improvements incorporating headings and logical grouping of multiple settings (TODO: ensure setting added in Limit amount of people in metadata search result #66 is in the right section/ revert the changes)

Testing:

• Rebased on top of the v9 branch, therefore testing not done yet. Build using github action fails here because of a change made from PersonType to "PersonKind" in 89c62c9
• Older version prior to v8 works fine, and has been tested personally.
• TODO: Need to verify compatibility with Limit amount of people in metadata search result #66

Opening a Draft PR for the following reasons:

1. Would it be a good idea to revert the change with naïve VA count filters (Limit amount of people in metadata search result #66) with this smarter system based on character roles? IMO limiting the raw number of results seems like taking a sledgehammer to the problem
2. UI feedback
3. Get more pairs of eyes on it for testing, questions about the PersonType -> PersonKind changes