[Cranelift] add commutative rules for min/max ops

[bongjunj]

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[cfallin]

Thanks, @bongjunj. As noted previously we generally don't add "commutativity without a further goal"; we do have some rules that push constants "to the right" and reassociate nested expressions for some operators so that const-prop can fire, but I don't see any such motivation here (in fact, your PR description is completely empty). The tests in this PR are similarly unenlightening: they don't highlight any cases where these optimizations enabled other rules to fire, for example. Could you describe the motivation in more detail? Thanks!

[bongjunj]

Sorry for the oversight on my end. I was seeing that the commutative/associative rules for iadd/isub/imul/... ops do not cover min/max operations. I have added the constant folding rules as well as the associative rules for min/max ops, and created a test scenario where the combinations actually reduces the number of min/max instructions.

[cfallin]

Thanks!

[cfallin]

@bongjunj it looks like there's a failing filecheck in CI only found once this hit the merge queue -- happy to re-merge once that's resolved...