chore: optimize GetPrebuiltWorkspaces query (#18717)

* Adds GetRunningPrebuiltWorkspacesOptimized query
* Runs both original and updated query side-by-side and logs diffs

coderd/database/dbauthz/setup_test.go

@@ -41,6 +41,8 @@ var skipMethods = map[string]string{
 	"Wrappers":       "Not relevant",
 	"AcquireLock":    "Not relevant",
 	"TryAcquireLock": "Not relevant",
+	// This method will be removed once we know this works correctly.
+	"GetRunningPrebuiltWorkspacesOptimized": "Not relevant",
 }
 
 // TestMethodTestSuite runs MethodTestSuite.