* fix: Avoid duplicate volume and mount name error for generic ephemeral volume as "work"
While manually testing configurations being documented in #1464, I discovered that the use of dynamic ephemeral volume for "work" directory was not working correctly due to the valiadation error.
This fixes the runner pod generation logic to not add the default volume and volume mount for "work" dir, so that the error disappears.
Ref #1464
* e2e: Ensure work generic ephemeral volume to work as expected
* Enhance RunnerSet to optionally retain PVs accross restarts
This is our initial attempt to bring back the ability to retain PVs across runner pod restarts when using RunnerSet.
The implementation is composed of two new controllers, `runnerpersistentvolumeclaim-controller` and `runnerpersistentvolume-controller`.
It all starts from our existing `runnerset-controller`. The controller now tries to mark any PVCs created by StatefulSets created for the RunnerSet.
Once the controller terminated statefulsets, their corresponding PVCs are clean up by `runnerpersistentvolumeclaim-controller`, then PVs are unbound from their corresponding PVCs by `runnerpersistentvolume-controller` so that they can be reused by future PVCs createf for future StatefulSets that shares the same same StorageClass.
Ref #1286
* Update E2E test suite to cover runner, docker, and go caching with RunnerSet + PVs
Ref #1286
This feature flag was provided from ARC to runner container automatically to let it use `--ephemeral` instead of `--once` by default. As the support for `--once` is being dropped from the runner image via #1384, we no longer need that.
Ref #1196
