The class will be used to build memory-efficient objects (int arrays)
used to queue ConnectivityService callbacks while an app is frozen.
This is very similar to an ArrayList<Pair<Short, Short>>, but avoids
object boxing which would use a lot more memory.
This is intended to be used by ConnectivityService both as a builder,
and as a utility to read lists of callbacks that it stores. Long-lived
references to the CallbackQueue would not be kept to minimize memory
usage; only the array returned by toArray needs to be stored.
Test: atest
Bug: 327038794
Bug: 279392981
Change-Id: I187ea15d14dfd160e577e9e9e87b1aded27b1938
c3621e6012