[clang] Refactor `IdentifierInfo::ObjcOrBuiltinID` (#71709)

This patch refactors how values are stored inside
`IdentifierInfo::ObjcOrBuiltinID` bit-field, and annotates it with
`preferred_type`. In order to make the value easier to interpret by
debuggers, a new `ObjCKeywordOrInterestingOrBuiltin` enum is added.
Previous "layout" of this fields couldn't be represented with this new enum,
because it skipped over some arbitrary enumerators, so a new "layout"
was invented, which is reflected in `ObjCKeywordOrInterestingOrBuiltin` enum. I
believe the new layout is simpler than the new one.