Move builder_spec, [dm|nanobench]_flags, builder_name_schema to recipes

- builder_name_schema becomes its own recipe module.
- builder_spec, dm, and nanobench flags move into vars module.
- recipe expectation diffs include:
  - no more buildbot_spec.py step
  - "real" dm and nanobench flags, instead of --dummy-flags
  - some inconsequential stuff in visualbench, which is removed anyway.

BUG=skia:5578
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2215803002

Review-Url: https://codereview.chromium.org/2215803002
87 files changed