[mlir][vector] Order parallel indices before transposing the input in multireductions

The current code does not preserve the order of the parallel
dimensions when doing multi-reductions and thus we can end
up in scenarios where the result shape does not match the
desired shape after reduction.

This patch fixes that by ensuring that the parallel indices
are in order and then concatenates them to the reduction dimensions
so that the reduction dimensions are innermost.

Differential Revision: https://reviews.llvm.org/D104884