WIP towards revoking upstream refresh tokens during GC

- Discover the revocation endpoint of the upstream provider in
  oidc_upstream_watcher.go and save it into the cache for future use
  by the garbage collector controller
- Adds RevokeRefreshToken to UpstreamOIDCIdentityProviderI
- Implements the production version of RevokeRefreshToken
- Implements test doubles for RevokeRefreshToken for future use in
  garbage collector's unit tests
- Prefactors the crud and session storage types for future use in the
  garbage collector controller
- See remaining TODOs in garbage_collector.go

internal/supervisor/server/server.go

@@ -124,6 +124,7 @@ func prepareControllers(
 		NewManager().
 		WithController(
 			supervisorstorage.GarbageCollectorController(
+				dynamicUpstreamIDPProvider,
 				clock.RealClock{},
 				kubeClient,
 				secretInformer,