Replace flagset crate with simple bools

[NickCondron]

flagset crate was used for only 4 separate bools which is probably overkill. This change removes a dependency and simplifies the code

[encounter]

I'm thinking this could just be an enum. The symbols will either be Global, Global|Weak, Global|Common or Local.

[ribbanya]

Nested enum can also work, if the semantics are important enough.

enum ObjSymbolScope {
   Global(ObjSymbolGlobalSubtype),
   Local,
}

enum ObjSymbolGlobalSubtype {
  None,
  Weak,
  Local,
}

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I definitely didn't notice the year on the dates.

[encounter]

I'll likely be merging these types with decomp-toolkit's eventually, which would conflict with this idea. Regardless, thanks for the cleanup PRs!