[MLIR][Vector] Refactor tests for contract -> OP transforms (4/N) (#73807)

This patch refactors tests for:

    vector.contract -> vector.outerproduct

for matvec operations (b += Ax). Summary of changes:
  * add 2 missing cases (masked + scalable) when the operation kind is
    `maxf`.

This is a part of a larger effort to add cases with scalable vectors to
tests for the Vector dialect.

Implements #72834.