evolvecmd: fix broken `evolve --continue` ran after `next --evolve`
Recent series broke `evolve --continue`in cases when run after `hg next
--evolve`. The previous patch adds test demonstarting the broken behaviour, this
patch fixes that by storing the command which leads us to evolve --continue in
the evolvestate.
tests: add test showing `evolve --continue` after `next --evolve` is broken
Recent series fixing `hg evolve --continue` break the continue functionality
after a conflicting `hg next --evolve`. This patch adds a test to demonstrate
that. It will be fixed in the upcoming patch.