Auto merge of #80459 - mark-i-m:or-pat-reg, r=petrochenkov

Implement edition-based macro :pat feature

This PR does two things:
1. Fixes the perf regression from https://github.com/rust-lang/rust/pull/80100#issuecomment-750893149
2. Implements `:pat2018` and `:pat2021` matchers, as described by `@joshtriplett`  in https://github.com/rust-lang/rust/issues/54883#issuecomment-745509090 behind the feature gate `edition_macro_pat`.

r? `@petrochenkov`

cc `@Mark-Simulacrum`

compiler/rustc_span/src/symbol.rs

@@ -470,6 +470,7 @@ symbols! {
         dropck_parametricity,
         dylib,
         dyn_trait,
+        edition_macro_pats,
         eh_catch_typeinfo,
         eh_personality,
         emit_enum,
@@ -808,6 +809,8 @@ symbols! {
         partial_ord,
         passes,
         pat,
+        pat2018,
+        pat2021,
         path,
         pattern_parentheses,
         phantom_data,