evolve: add test for content-div where one div cset rebased backward

This patch adds a test coverage for the resolution of a case where one
side amended some content changes and other side moved backward and
created content-divergence.
8 jobs for topic/default/khanchi-gca in 7 minutes and 36 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Test
passed #125753
checks-py2

00:01:57

passed #125754
checks-py3

00:03:37

passed #125759
doc

00:00:23

manual #125752
allowed to fail manual
pytype
passed #125755
tests-py2-cext

00:04:12

passed #125756
tests-py2-pure

00:06:48

passed #125757
tests-py3-cext

00:06:33

passed #125758
tests-py3-pure

00:07:35