[mlir][linalg] Add e2e test for linalg.mmt4d + pack/unpack (#84964)

This is a follow-up for #81790. This patch basically extends:

  * test/Integration/Dialect/Linalg/CPU/mmt4d.mlir

with pack/unpack ops so that to overall computation is a matrix
multiplication (as opposed to linalg.mmt4d). For comparison (and to make
it easier to verify correctness), linalg.matmul is also included in the
test.