c28940e49d
Use a `Field` in `ConstraintCategory::ClosureUpvar`
As part of #90317, we do not want `HirId` to implement `Ord`, `PartialOrd`. This line of code has made that difficult
1b27144afc/compiler/rustc_borrowck/src/region_infer/mod.rs (L2184)
since it sorts a [`ConstraintCategory::ClosureUpvar(HirId)`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/mir/enum.ConstraintCategory.html#variant.ClosureUpvar).
This PR makes that variant take a [`Field`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/mir/struct.Field.html) instead.
r? `@nikomatsakis`