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