[clang] [Clang] Fix various bugs in alias CTAD transform (PR #132061)

[via cfe-commits]

================
@@ -1348,6 +1348,16 @@ std::optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
   return std::nullopt;
 }
 
+static TemplateArgument
+getPackSubstitutedTemplateArgument(Sema &S, TemplateArgument Arg) {
----------------
cor3ntin wrote:

`getSubstitutedTemplateArgumentPattern`  would be a better name. Please add a comment too

https://github.com/llvm/llvm-project/pull/132061