help: categorizing evolve and topic commands

This makes them show up under the right categories in 'hg help'.

Differential Revision: https://phab.mercurial-scm.org/D6999
2 jobs for topic/default/help_categories in 13 minutes and 26 seconds (queued for 7 seconds)
Status Name Job ID Coverage
  Test
passed flake8 #29187

00:00:17

passed tests #29188

00:13:08