ART: Add --dump-pass-timings compiler option.

This replaces the old --dump-passes option removed in
    https://android-review.googlesource.com/549200 .
Using --dump-timing for timing optimization passes makes
the high level timings useless, so return to using two
different options for these.

Test: Manually run dex2oat with --dump-timings,
      --dump-pass-timings and both.
Change-Id: Iddc4cfee35652fb493656e7d6081a898c2894f72