Support breakpoints on APX instructions

[anthonycanino]

Per #89705 and #104514 some similar work will be needed for APX debugging support in .NET.

The items I have are:

1. Make sure new registers are handled in the context like structures.
2. Handle decoding of additional new prefixes (REX2, extended EVEX).
3. Address any RIP instructions.

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[BruceForstall]

It looks like #104514 is independent of debugging (maybe it is only used on non-Windows debugging code paths?), and can be done by Intel.

The debugging-specific changes (similar to #89705) should be implemented by Microsoft.

[BruceForstall]

I believe this is done, until proven otherwise.