Issue 59415 (#59497)

Issue 59415 (#59497)

* Undo shift-back with AVX register for block copy, use GPR for remainder. Results in better perf

* Cleanup

* Use GPR instead of SIMD for block init remainder

* JIT formatting

* More JIT formatting

* Fixed local jit-format.bat, formatting should be correct now

* Using older jit-format.bat on backup machine

* Revert "Using older jit-format.bat on backup machine"

This reverts commit b0e081714cab85aa9fd5cec53375745fa5c68fb2.

* Revert "Fixed local jit-format.bat, formatting should be correct now"

This reverts commit 39c3f2ff22e8c7abfa7108b2506ecb10c249c320.

* Revert "More JIT formatting"

This reverts commit 237ce3122294201abbcfd2c52cbb1ebccc4f4462.

* Revert "JIT formatting"

This reverts commit 3191bd4075fc1c93ac9eeb0af08e367702d3d804.

* Undo weird JIT formatting, add note for YMM->XMM step down