Canonicalization of triton reduce with select to arith min/max

[mitekoth]

This PR introduces a pattern rewrite that simplifies triton::ReduceOp bodies containing arith.select operations based on floating-point comparisons. The transformation replaces select-based logic with equivalent min/max operations, improving IR canonicalization and enabling further optimization.

Supported Transformations:
select(cmpf ogt a, b), a, b → arith.maxf(a, b)
select(cmpf olt a, b), a, b → arith.minf(a, b)
select((cmpf ogt a, b) || cmpf une a, a), a, b → arith.maximumf(a, b)
select((cmpf olt a, b) || cmpf une a, a), a, b → arith.minimumf(a, b)
Applying this transformation before the ReduceOp converter runs allows the natural lowering of tt.reduce to linalg.reduce; the motivational use case was from a torch-inductor spit out Triton kernel which consisted of this complex pattern in the reduction body and did not allow the ReduceOp to get lowered to the linalg dialect.

PR cloned from microsoft/triton-shared#361

[mitekoth]

@nhat-nguyen This PR was already reviewed in the Microsoft repo. Let me know if any additional changes are needed so that this can be merged asap. Thanks!

[mitekoth]

Thanks for the review. Please feel free to merge the PR 😄