[mlir][linalg] fix crash in vectorization of elementwise operations

The current vectorization logic implicitly expects "elementwise"
linalg ops to have projected permutations for indexing maps, but
the precondition logic misses this check. This can result in a
crash when executing the generic vectorization transform on an op
with a non-projected permutation input indexing map. This change
fixes the logic and adds a test (which crashes without this fix).

Differential Revision: https://reviews.llvm.org/D127000