Auto merge of #54260 - maxdeviant:public-scope-fields, r=petrochenkov

Make rustc::middle::region::Scope's fields public

This PR makes the following changes to `rustc::middle::region::Scope`:

- [x] Makes `region::Scope`'s fields public
- [x] Removes the `impl Scope` block with constructors (as per [this comment](https://github.com/rust-lang/rust/pull/54032#discussion_r216618208))
- [x] Updates call sites throughout the compiler

Closes #54122.

diff --cc src/librustc_borrowck/borrowck/mod.rs
Simple merge