inference: make `limit::Int` as a caching key of `CachedMethodTable` (#46799)
Sometimes `Core.Compiler.findall(::Type, ::CachedMethodTable; limit::Int)`
is called with different `limit` setting (in particularity
`return_type_tfunc` calls it with `limit=-1`). The query should return
different results given different `limit` settings, so its cache should
also have different keys per different `limit` settings.
fix #46722