[_fe_analyzer_shared] Support intersection types in exhaustiveness

This adds handling of type variables with bounds and intersection types
in exhaustiveness checking. These are handled using [WrappedStaticType]s
where the type variable is the implied type and the bound is the
wrapped type from which the subtypes are computed, thereby supporting
sealed types in the bounds.

The change also includes some cleanups a fixes found during
implementation, amongst these a fix to no longer cache the map/list
type identities objects. These were not used as identities, similar to
the value identities used for enum and bool values, but instead as
restrictions on the the static type. These have therefore been renamed
to Map/ListTypeRestriction to reflect that.

Closes https://github.com/dart-lang/language/issues/2878
Closes #51819

Change-Id: I56e94e4f0dc6695288ab978687d8c95835535b8d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/291220
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>