phases: use revision number in analyze_remote_phases
Same logic as the previous change to `new_heads`, see rationnal there.
This avoids a small number of `nodes -> revs` conversion speeding thing up in
the 100 milliseconds order of magnitude for the worses cases. However, the rest
of the logic is noisy enough that it hardly matters for now.
ERROR: FIXME: This is a known failure of filelog.size for data starting with \1\n
OK.