Add peephole optimization to replace x86 SIMD instructions with smaller equivalents

[saucecontrol]

As pointed out in #112728 (comment), there are some SIMD instructions that have equivalents with smaller encoding.

For example, pupcklpd can be replaced with movlhps, which is 1 byte smaller, under the following conditions:

1. both operands are from register
2. VEX encoding is not supported

Similarly, vpermilps can be replaced with the smaller vpshufd if mixing float and integer domain instructions is not a concern.

llvm has logic that identifies some of these replacements here

cc @tannergooding

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[JulieLeeMSFT]

@BruceForstall, please triage this issue.

[BruceForstall]

cc @anthonycanino