[clang][NewPM] Add -fno-experimental-new-pass-manager to tests


[clang][NewPM] Add -fno-experimental-new-pass-manager to tests

As per the discussion on D58375, we disable test that have optimizations under
the new PM. This patch adds -fno-experimental-new-pass-manager to RUNS that:

  • Already run with optimizations (-O1 or higher) that were missed in D58375.
  • Explicitly test new PM behavior along side some new PM RUNS, but are missing this flag if new PM is enabled by default.
  • Specify -O without the number. Based on getOptimizationLevel(), it seems the default is 2, and the IR appears to be the same when changed to -O2, so update the test to explicitly say -O2 and provide -fno-experimental-new-pass-manager`.

Differential Revision: https://reviews.llvm.org/D63156