upgrade: explicitly warn when a `--no-xxx` flag is overwritten
Some format upgrade/downgrades -needs- revlog to be recomputed. So we now
detect that individually and warn when it contradict explicitly passed flag.
This is part of a larger series to make `debugupgraderepo` smarter about which
revlog it picks by default.
Differential Revision: https://phab.mercurial-scm.org/D11869