[NewPM] Add ExtraVectorizerPasses support

As it looks like NewPM generally is using SimpleLoopUnswitch
instead of LoopUnswitch, this patch also use SimpleLoopUnswitch
in the ExtraVectorizerPasses sequence (compared with LegacyPM
which use the LoopUnswitch pass).

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D95457