Update build setup for run-support project (2.3.x)

Some groundwork for forked runner.

Simplify the project setup and cross-building for the run-support projects.

Fix the sbt io dependencies so that cross-compiled versions are used.
Also mark these as provided so that the current sbt versions are used at runtime.

Remove the publish local step that was added for scripted tests when run-support was added.
For ./runtests it will publish again, and the publishing of the docs project rebuilds the aggregated scaladoc and javadoc.
So back to simply requiring a manual publish local of the projects outside of the sbt plugin.