[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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@364066 91177308-0d34-0410-b5e6-96231b3b80d8