evolve: wrap the more modern wireprotov1server._capabilities()

This function is recommended for wrapping instead of capabilities(). It also
needs less code from extensions, as this patch demonstrates.

The function exists since 982f13bef503, which is 2014, so we can rely on this
function to be present in any modern Mercurial.
8 jobs for topic/default/capabilities-underscore in 4 minutes and 43 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed checks-py2 #204660

00:01:01

passed checks-py3 #204661

00:01:49

passed doc #204666

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manual pytype #204659
allowed to fail manual
passed tests-py2-cext #204662

00:04:37

passed tests-py2-pure #204663

00:03:00

passed tests-py3-cext #204664

00:04:43

passed tests-py3-pure #204665

00:04:00