JIT: Switch optOptimizeLayout to pre-layout optimization phase

[amanasifkhalid]

Part of #107749. This is part of my broader goal of phasing out fgReorderBlocks entirely, but there are a few transformations we may want to do right before block layout. In particular, I noticed in #113108 (comment) that some regressed benchmarks have loops with unconditional backedges; in the absence of better loop inversion, we might want to run our unconditional-to-conditional branch duplication optimization right before layout to improve branch behavior in loops. We can put such optimizations in this pre-layout phase.

I'm trying to keep diffs to a minimum in this PR, but this was a good opportunity to run switch recognition before switch opts.

[Copilot]

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[amanasifkhalid]

cc @dotnet/jit-contrib, @AndyAyersMS PTAL. Small diffs on x64 from moving switch recognition a phase earlier. On x86, we no longer explicitly move cold try regions since we can rely on layout to do that, but that shouldn't have diffs. We also save a bit of TP from skipping fgReorderBlocks. Thanks!