Implement new effects desugaring
cc `@rust-lang/project-const-traits.` Will write down notes once I have finished.
* [x] See if we want `T: Tr` to desugar into `T: Tr, T::Effects: Compat<true>`
* [x] Fix ICEs on `type Assoc: ~const Tr` and `type Assoc<T: ~const Tr>`
* [ ] add types and traits to minicore test
* [ ] update rustc-dev-guide
Fixes#119717Fixes#123664Fixes#124857Fixes#126148