Rollup merge of #118157 - Nadrieril:never_pat-feature-gate, r=compiler-errors

Add `never_patterns` feature gate

This PR adds the feature gate and most basic parsing for the experimental `never_patterns` feature. See the tracking issue (https://github.com/rust-lang/rust/issues/118155) for details on the experiment.

`@scottmcm` has agreed to be my lang-team liaison for this experiment.

compiler/rustc_hir_analysis/src/check/region.rs

@@ -662,6 +662,7 @@ fn resolve_local<'tcx>(
             PatKind::Ref(_, _)
             | PatKind::Binding(hir::BindingAnnotation(hir::ByRef::No, _), ..)
             | PatKind::Wild
+            | PatKind::Never
             | PatKind::Path(_)
             | PatKind::Lit(_)
             | PatKind::Range(_, _, _) => false,