[NewPM] Handle -simplifycfg in opt

Summary:
-simplifycfg is the legacy pass name for SimplifyCFGPass.

There is already -simplify-cfg in FUNCTION_PASS_WITH_PARAMS which
handles options for SimplifyCFGPass. Maybe that should be renamed to
-simplifycfg as well?

This reduces the number of check-llvm failures under NewPM from 2619 to 2392.

Reviewers: hans, leonardchan, asbirlea, ychen

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D82421