Contribution docs, the PR template and the workflows that talk to the
testing repository use the new name. Migration PRs are matched by either
name, and three license headers pointed at contributor forks.
Replaces the misc/build.func bootstrap with the two-root core loader.
No other change: the engine contract (var_*, update_script, start,
build_container, description) is identical on both engines.
versitygw.sh additionally gains a trailing newline; it lacked one.
With this batch every ct/ script is on the core engine.