Tune LSRA with APX EGPR

[anthonycanino]

This task is to tune LSRA to use APX EGPRs more efficiently (if applicable). As part of this effort, we will do some further investigation into the quality of the code that is generated with the EGPRs and investigate if/what further improvements can be made to the codegen.

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[DeepakRajendrakumaran]

Have looked into this for regression with additional registers. One issue which stood out was cse heuristics- especially the moderate threshold. We do not differentiate between intervals with function calls(prefers callee saved) vs intervals with no function calls(prefers callee trashed). This causes some regressions with APX since it creased the number of Callee Trashed registers only. Tanner had a relevant comment here

I'm trying to tweak the heuristic here and understand if it helps.

[JulieLeeMSFT]

Anthony: Ongoing discussions at #117560, if an optimization is found, RC1/RC2 target, likely .NET 11 due to larger changes.

[JulieLeeMSFT]

Moved to .NET 11.