JIT: Allow compaction of blocks with switch predecessors

[amanasifkhalid]

Now that switch successor edge redirection is trivial, we can compact blocks with switch predecessors without worrying about invalidating the entire switch successor map.

[Copilot]

Pull Request Overview

This PR refactors the JIT by allowing compaction of blocks even if they have switch predecessors, taking advantage of trivial switch successor edge redirection.

• Removed the check that prevented block compaction when a switch predecessor was present.
• Simplified the logic in fgCanCompactBlock() to always return true when no blocking conditions besides the removed check exist.

Comments suppressed due to low confidence (1)

src/coreclr/jit/fgopt.cpp:838

• Update the function's comment to reflect that compaction is now allowed for blocks with switch predecessors, ensuring that future maintainers understand this behavioral change.

        return false;

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[amanasifkhalid]

cc @dotnet/jit-contrib, @AndyAyersMS PTAL. Small diffs. Thanks!