perf: instantiate constructor types through the level cache in `isUnitLikeType`

This PR makes `isUnitLikeType` instantiate the universe parameters of a structure's constructor type with `Core.instantiateTypeLevelParams`, which computes the same expression and caches it. `isUnitLikeType` instantiated the whole constructor type on each call, and it runs often on types with free variables or metavariables, where the result cache of `isDefEqUnitLike` does not apply.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>