Adds access to the name lookup table in name scopes. This is so that we
can quickly check access during name lookup without resolving the entity
itself. Does this for names in general, but does not implement handling
for entity-scoped names, only namespace-scoped names (where they're
essentially just not exported).
Excludes `private` names from exports. Although names should be
accessible to `impl` files, that's not implemented here because we'll
probably want to do it by directly copying name lookup tables.
Mirroring #4003 for NodeCategory.
Note we template a lot more on NodeCategory's enum, so this is a
slightly more awkward delta.
Also, switch from Enum in KeywordModifierSet to RawEnumType for
consistency with EnumBase. The templating on NodeCategory had me
thinking about that more.
This is primarily to avoid the use of `!!` in code, trying not to create
too much code as a result (obviously still a net increase). Also
refactoring to its own file to make the enum easier to find.
Note, NodeCategory does similar, I might propose similar there if
everyone's good with the API. However, that's just two, so creating
something like enum_base felt like too much.
josh11bandJosh L
David BlaikieandJon Ross-Perkins