rewriteutil: use precheck from core if recent enough

This commit makes the evolve extension's `rewriteutil.precheck()`
simply delegate to the same function from Mercurial core, if that
function is deemed recent enough. The way I made that check is by
looking for `rewriteutil.find_new_divergence_from()`. That means that
there's a range of commits (ba6881c6::8125bcd2^) where the user would
see less detailed error messages if they are running with an hg
version from that range (there are no released versions in that
range).

As you can see in the tests, switching to core's version of the
function mostly affects error messages and exit codes.
8 jobs for topic/default/core-precheck in 7 minutes and 57 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Test
passed checks-py2 #208743

00:01:03

passed checks-py3 #208744

00:01:08

passed doc #208749

00:00:18

manual pytype #208742
allowed to fail manual
passed tests-py2-cext #208745

00:07:34

passed tests-py2-pure #208746

00:03:02

passed tests-py3-cext #208747

00:07:21

passed tests-py3-pure #208748

00:07:49