[clang] [Sema] Warn about omitting deprecated enumerator in switch (PR #138562)

[Reid Kleckner via cfe-commits]

================
@@ -6767,6 +6767,9 @@ class Sema final : public SemaBase {
     };
     std::optional<InitializationContext> DelayedDefaultInitializationContext;
 
+    /// Whether evaluating an expression for a switch case label.
----------------
rnk wrote:

supernit: pack it with the contextual bools above, for both layout reasons and because it shows there's prior art

https://github.com/llvm/llvm-project/pull/138562