Allow disabling RunConfig appending project path

[MattSturgeon]

I'd like to have more control over run config names in sub-projects, for example something like:

allprojects {
  loom {
    runs {
      client {
        configName "Run ${project.path.replaceAll ':', ' '}"
        appendProjectPathToConfigName false
      }
      remove server
    }
  }
}

This PR adds that capability.

All tests passed when running :check locally.

I'd like to have introduced a test for both the default & modified behavior, however I'm a bit lost in your test suite and didn't want to spend much time on this PR without knowing how it'd be received.

If someone more knowledgeable would like to write a test or guide me through the process that'd be appreciated.