[clang] [clang][ASTImporter] Remove 'hasReturnTypeDeclaredInside' (PR #169504)

[Balázs Kéri via cfe-commits]

balazske wrote:

#162514 is the change where a new cycle detection support is added. This can find any cyclical import during import of a `FunctionDecl`. The old code tries to find the cyclical import conditions before the import process. This was not a robust solution, it is difficult to check for all possible cycle conditions, it was cause of more crashes because previously unknown import cycle paths. The new code detects the cycles during the import process and should find any cycle.

https://github.com/llvm/llvm-project/pull/169504