[clang] [Clang][CIR] Add vqshlud and vqshld AArch64 builtins (PR #190728)

[Andrzej Warzyński via cfe-commits]

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banach-space wrote:

For tests, could you follow the guidance outline here:
* https://github.com/llvm/llvm-project/issues/185382#issuecomment-4022508229

? In particular, 
* use `clang/test/CodeGen/AArch64/neon/intrinsics.c` instead of adding new test files,
* re-use the original tests from e.g. `lang/test/CodeGen/AArch64/neon-intrinsics.c` and other test files,
* follow the pre-existing formatting from `clang/test/CodeGen/AArch64/neon/`.

Thanks!

https://github.com/llvm/llvm-project/pull/190728