[clang] [clang][ASTImporter] skip TemplateTypeParmDecl in VisitTypeAliasTemplateDecl (PR #74919)

[Balázs Kéri via cfe-commits]

balazske wrote:

The problem may be related to the fact that template parameter declarations can have the `TranslationUnitDecl` as parent until the template (with these parameters) is finally created. In the temporary phase the object (`TemplateTypeParmDecl`) is found with lookup if it has the same name as an other imported object. Does the crash happen if in the test code the `TypeAliasTemplateDecl` is replaced with a plain `ClassTemplateDecl` or `FunctionTemplateDecl`? If yes the change is needed at these import functions too.

https://github.com/llvm/llvm-project/pull/74919