Automatic merge from submit-queue

Enable the garbage collector by default

Turning GC on by default.

Memory usage of GC is back to normal after #30943. The CPU usage is a little higher than the cap in scalability test (1.11 core vs. 1 core). This PR adjusted the default GC worker to 20 to see if that helps CPU usage.

@kubernetes/sig-api-machinery  @wojtek-t @lavalamp