[Target][Legalization]Add Tir Level Legalization Function Registration And Update Intrinsic Lowering Pass

[zxybazh]

This PR introduces tir level op legalization function registration to current tvm stack and injects the legalization function when no intrinsic lowering function is available. Currently the legalization functions are target-dependent. Previous legalization functions are migrated to the legelization function registry as well.

[junrushao]

@tqchen @zxybazh I am thinking if we should move the intrinsic registeration logic to src/tir/intrin, given it is part of TIR and is logically closer to IR manipulation

[zxybazh]

IMHO, the intrinsic lowering pass logic is already in src/tir and the intrinsic lowering ruls are more target dependent so I think it's okay if we keep those rules in src/target. However, since it's pure tir level manipulation, I would be fine if we want to move all intrinsic lowering and legalization rules to src/tir/intrin and src/tir/legalization, and manage them together. Would like to see how others think about it.

[junrushao]

@zxybazh The PR looks good. Please retrigger the CI :-)

[junrushao]

LGTM. I don't have much to comment unlike the previous two :-)

Thanks for the contribution!

[junrushao]

This PR looks good to me. @tqchen @anijain2305 @zhiics Please let me know if there are any further comments.