[clang] [Attributes] Support Attributes being declared as only supporting late parsing when passing an experimental feature flag (PR #88596)

[Dan Liew via cfe-commits]

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@@ -592,6 +592,46 @@ class AttrSubjectMatcherAggregateRule<AttrSubject subject> {
 
 def SubjectMatcherForNamed : AttrSubjectMatcherAggregateRule<Named>;
 
+// Late Attribute parsing mode enum
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delcypher wrote:

@rapidsna I renamed the `LateAttrParseKind` definitions and updated the comments explaining the semantics. Does this look right to you?

https://github.com/llvm/llvm-project/pull/88596