Support gradle run task for core plugins

[lukas-vlcek]

Is your feature request related to a problem? Please describe.

When working on a "core" plugins there does not seem to be OOTB support for the run tasks that would automatically deploy the plugin into testcluster.

Describe the solution you'd like

It would be useful to be able to do something like ./gradlew run --plugins "xx,yy" and get testcluster with core plugins xx and yy deployed.

Describe alternatives you've considered

I described a manual workaround here:
https://gist.github.com/lukas-vlcek/26fd54fb7ba25debb5b5c5c8c390ad79

Additional context

Core plugin authors would be 😄

[dbwiddis]

Sounds like a good idea!

[dblock]

#11844 has this implemented.