[mlir][spirv] Unify resources of different vector sizes

This commit extends UnifyAliasedResourcePass to handle the case
where aliased resources have different vector sizes. (It still
requires all scalar types to be of the same bitwidth.) This is
effectively reusing the code for handling different-bitwidth
scalar types.

Reviewed By: ThomasRaoux

Differential Revision: https://reviews.llvm.org/D130671