* eliminate heading for test kinds, of which there is now only one
* make the caches document have a single heading in the TOC
* break out mach commands into a separate document, add ./mach taskgraph morphed
* remove docs for YAML templates support (the .yml file wasn't actually
used -- I expect it was a merge leftover); these are still used for actions.yml,
but once that is gone the code should be removed, too.
* break try out into its own document, edit to distinguish "how to run try"
from "how to generate config"
MozReview-Commit-ID: 76ZopWA9TPL
--HG--
extra : rebase_source : 6946d866f9df6eec591b9a05ddedc6467dd69e4b
