[clang] Turn 'counted_by' into a type attribute and parse it into 'CountAttributedType' (PR #78000)

[Yeoul Na via cfe-commits]

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@@ -2000,6 +2001,21 @@ class alignas(TypeAlignment) Type : public ExtQualsTypeCommonBase {
     unsigned NumExpansions;
   };
 
+  class CountAttributedTypeBitfields {
+    friend class CountAttributedType;
+
+    LLVM_PREFERRED_TYPE(TypeBitfields)
+    unsigned : NumTypeBits;
+
+    /// The limit is 15.
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rapidsna wrote:

Thanks! I added `static_assert` and removed the comment.

https://github.com/llvm/llvm-project/pull/78000