[mlir][Vector] Refactor vector distribution and fix an issue related to non-homogenou...

[mlir][Vector] Refactor vector distribution and fix an issue related to non-homogenous transfer indices.

Running: `mlir-opt -test-vector-warp-distribute=rewrite-warp-ops-to-scf-if -canonicalize -verify-each=0`.

Prior to this revision, IR resembling the following would be produced:
```
  %4 = "vector.load"(%3, %arg0) : (memref<1x32xf32, 3>, index) -> vector<1x1xf32>
```
This fails verification since it needs 2 indices to load but only 1 is provided.

Differential Revision: https://reviews.llvm.org/D133106