[Pipeline] Fix Python packaging pipeline failures (#29200)
### Description
PR that introduced issue:
https://github.com/microsoft/onnxruntime/pull/29064
Fixes in this PR:
1) Add relevant platform guard in some tests that was previously missing
2) Added the new AVX512 headers that host the kernels to their right
location within the cmake file grouping - previously they were placed in
AVX2 grouping (ultimately the TU that included those headers were
compiled with AVX512 flags - so no harm was done). This fix is more
pedantic than fixing a real issue. The lone .cpp file in that list
didn't include any intrinsics manually but the compiler might use AVX512
now for auto-vectorization with the shuffling. Since that file contains
only the pre-packing functions that are used in production, it is safe.
The "scalar" kernel implementation in that file is mostly a test oracle
- nothing else
Sample failed run (before PR):
https://aiinfra.visualstudio.com/Lotus/_build/results?buildId=1268723&view=results
Sample successful run (with PR):
https://aiinfra.visualstudio.com/Lotus/_build/results?buildId=1273196&view=results
### Motivation and Context
Fix Python packaging pipeline
