[PassManager] restore early-cse to vector cleanup

As noted in D80236 - the early-cse pass was included here before:
D75145 / rG71a31688
But it got moved outside of the "extra" option there, then it
got dropped while adjusting -vector-combine:
rG6438ea45
rG57bb4787

So this is restoring the behavior and adding a test to prevent
accidental changes again. I don't see an equivalent option for
the new pass manager.