Add a special case for erase(begin(), end()) to reset the control bytes. The motivation is to avoid potentially expanding the table unnecessarily later.

Note: I prefer doing this as a special case in erase(iterator, iterator) rather than special casing erase(iterator) for size==1 because IIUC that changes the time complexity of erase(iterator) from O(1) to O(N) and in pathological cases, it could change loops from O(N) to O(N^2).
PiperOrigin-RevId: 549661855
Change-Id: I8603324260f51a98809db32f840ff09f25cf2481