[llvm] [llvm-exegesis][AArch64] Disable pauth and ldgm as unsupported instructions (PR #132346)

[via llvm-commits]

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+# REQUIRES: aarch64-registered-target
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lakshayk-nv wrote:

I originally named it `err_skip_illegal_Instruction.s` to indicate it's a test case for error skipping behavior, but you're right that `skip_unsupported_instructions.s` would be more accurate since these instructions are unsupported rather than illegal. I will push required changes.

Btw, Can you weigh in for checking other skipped errors (`isPseudo`, `isReturn` etc.). 
Does it make sense to check them also in this testfile, (just for completeness) ?

https://github.com/llvm/llvm-project/pull/132346