* use Array.Empty() where instead of allocating new zero-length arrays
* structure for loops in a way that the JIT will elide array/Span bounds checking
* avoiding function calls in for loop condition tests
* avoid LINQ in a hot path
* conform with code style
* fix mistake in GetNextWaitingObject()
* fix GetNextWaitingObject() possibility of returning null if all list items have TimePoint == long.MaxValue
* make GetNextWaitingObject() behave FIFO behavior for multiple items with the same TimePoint
