This adds a generated-resources dir that the plugin properties are
generated into. This must be outside of the build dir, since intellij
has build as "excluded".
closes#14392
The RR gradle plugin is at
https://github.com/randomizedtesting/gradle-randomized-testing-plugin.
However, we currently have a copy of this, since the plugin is still in
heavy development. This change moves the files around so they can be
copied directly from the elasticsearch fork to that repo, for ease of
syncing.
