[mlir][mesh] Dedublicate iterator type and partial type information (#81920)

The two types duplicated mostly the same values.
Here they are decomposed to carry orthogonal and complimentary
information.

Use `utils::IteratorType` instead of `mesh::IteratorType`. It now has
only parallel and reduction values.

Rename `Partial` to `ReductionKind`.

Add `getReductionLoopIteratorKinds` method to `ShardingInterface`.