Motivation:
The executor chooser should pluck executors in round-robin, but at the 32-bit
overflow boundary, the round-robin sequence was disrupted when the number of
executors are not a power of 2.
Modification:
Changed the index counter from a 32-bit to a 64-bit long. The overflow bug is
still technically there, but it now takes so long to reach that it will never
happen in practice. For example, 2^63 nanoseconds is almost 300 years.
Result:
The round-robin behaviour for all EventExecutorChoosers is now preserved in
practice.
This fixes#10423.
cfeda0fef2