Auto merge of #82898 - oli-obk:tait_🧊, r=nikomatsakis

Auto merge of #82898 - oli-obk:tait_🧊, r=nikomatsakis

Add a `min_type_alias_impl_trait` feature gate

This new feature gate only permits type alias impl trait to be constrained by function and trait method return types. All other possible constraining sites like const/static types, closure return types and binding types are now forbidden and gated under the `type_alias_impl_trait` and `impl_trait_in_bindings` feature gates (which are both marked as incomplete, as they have various ways to ICE the compiler or cause query cycles where they shouldn't).

r? `@nikomatsakis`

This is best reviewed commit-by-commit