[APX] Get ThreadContext for APX extended registers

[Ruihan-Yin]

APX will introduce 16 new general-purpose registers (EGPRs).

Similar to #104514, we should also make sure those new registers are part of the context when needed.

[Ruihan-Yin]

Hi @BruceForstall , this will be needed for the APX support, can you please add the tag to this issue? Thanks!

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[Ruihan-Yin]

Hi @BruceForstall, with a closer observation into #104514, the PR added the exception handling for AVX/AVX512 related registers under HAVE_MACH_EXCEPTION is set, so it is for Apple related environment, and I think there will never be a case where Apple will use APX, since they are with their own processors now.

If you agree with the observation, I'd suppose it is safe to close this issue as no changes/PR needed.

[BruceForstall]

That looks correct. Thanks for investigating. I'll close this.