evolve: use repo.setparents() instead of repo.dirstate.setparents()
setparents() was added to localrepository class in 2012, and now we finally
have some differences between calling repo.setparents() vs
repo.dirstate.setparents(): _quick_access_* things, introduced in hg 5.3.
This patch fixes an actual quick-access desync problem where repo[b'.'] would
be different from repo.dirstate.p1(), as demonstrated by
test-evolve-phase-divergence.t when ran on hg 5.3rc0 and later.
Modified _uncommitdirstate() too, because it is used in dirstatedance(), which
sometimes follows repo.setparents() calls.