[X86] LowerShiftByScalarImmediate - move shl(x,1) -> add(freeze(x),freeze(x))...

[X86] LowerShiftByScalarImmediate - move shl(x,1) -> add(freeze(x),freeze(x)) to X86FixupInstTunings (#161007)

Avoid the shl(x,1) -> add(freeze(x),freeze(x)) if the shift-imm if
legal, and leave it to X86FixupInstTunings.

Helps avoid missed optimisations due to oneuse limits, avoids
unnecessary freezes and allows AVX512 to fold to mi memory folding
variants.

Fixes #161006