[WholeProgramDevirt][NewPM] Add NPM testing path to match legacy pass

The legacy pass's default constructor sets UseCommandLine = true and
goes down a separate testing route. Match that in the NPM pass.

This fixes all tests in llvm/test/Transforms/WholeProgramDevirt under NPM.

Reviewed By: ychen

Differential Revision: https://reviews.llvm.org/D88588