Auto merge of rust-lang#79278 - mark-i-m:stabilize-or-pattern, r=nikomatsakis

Stabilize or_patterns (RFC 2535, 2530, 2175)

closes rust-lang#54883

This PR stabilizes the or_patterns feature in Rust 1.53.

This is blocked on the following (in order):
- [x] The crater run in rust-lang#78935 (comment)
- [x] The resolution of the unresolved questions and a second crater run (rust-lang#78935 (comment))
    - It looks like we will need to pursue some sort of edition-based transition for `:pat`.
- [x] Nomination and discussion by T-lang
- [x] Implement new behavior for `:pat` based on consensus (rust-lang#80100).
- [ ] An FCP on stabilization

EDIT: Stabilization report is in rust-lang#79278 (comment)

Author: bors

alloc/src/lib.rs

@@ -118,7 +118,7 @@
 #![feature(nonnull_slice_from_raw_parts)]
 #![feature(auto_traits)]
 #![feature(option_result_unwrap_unchecked)]
-#![feature(or_patterns)]
+#![cfg_attr(bootstrap, feature(or_patterns))]
 #![feature(pattern)]
 #![feature(ptr_internals)]
 #![feature(rustc_attrs)]

core/src/lib.rs

@@ -126,7 +126,7 @@
 #![feature(exhaustive_patterns)]
 #![feature(no_core)]
 #![feature(auto_traits)]
-#![feature(or_patterns)]
+#![cfg_attr(bootstrap, feature(or_patterns))]
 #![feature(prelude_import)]
 #![cfg_attr(not(bootstrap), feature(ptr_metadata))]
 #![feature(repr_simd, platform_intrinsics)]

std/src/lib.rs

@@ -297,7 +297,7 @@
 #![feature(nonnull_slice_from_raw_parts)]
 #![feature(once_cell)]
 #![feature(auto_traits)]
-#![feature(or_patterns)]
+#![cfg_attr(bootstrap, feature(or_patterns))]
 #![feature(panic_info_message)]
 #![feature(panic_internals)]
 #![feature(panic_unwind)]