Bump chalk
There's a bug in current chalk that prevents us from properly supporting GATs, which is supposed to be fixed in v0.86. Note the following:
- v0.86 is only going to be released next Sunday so I'll keep this PR as draft until then.
- This doesn't compile without https://github.com/rust-lang/chalk/pull/779, which I hope will be included in v0.86. I confirmed this compiles with it locally.
Two breaking changes from v0.84:
- `TypeFolder` has been split into `TypeFolder` and `FallibleTypeFolder` (https://github.com/rust-lang/chalk/pull/772)
- `ProjectionTy::self_type_parameter()` has been removed (https://github.com/rust-lang/chalk/pull/778)