revset: ensure we have loaded phases data in '_notpublic()' If we are the very first rev access (or if the phase cache just got invalidated) the phasesets will be None even if we support the native computation. So we explicitly trigger a computation if needed. This was not an issue before because requesting any phase information would have triggered such computation.

phase: rename getphaserevs to loadphaserevs This function is: - already loading the data in place, - used once in the code. So we drop the return value and change the name to make this obvious. We keep the function public because we'll have to use it in revset.