[mlir][Linalg] Enable vectorization of explicit broadcasts

This patch teaches `isProjectedPermutation` and `inverseAndBroadcastProjectedPermutation`
utilities to deal with maps representing an explicit broadcast, e.g., (d0, d1) -> (d0, 0).
This extension is needed to enable vectorization of such explicit broadcast in Linalg.

Reviewed By: pifon2a, nicolasvasilache

Differential Revision: https://reviews.llvm.org/D111563