rhg: fix bugs around [use-dirstate-tracked-hint] and auto-upgrade

• make rhg support the [dirstate-tracked-key-v1] requirement. I believe rhg never changes the tracked file set, so it's OK that it doesn't have any logic for writing this file.

• fix the name of [format.use-dirstate-v2.automatic-upgrade-of-mismatching-repositories] config option in rhg, which makes rhg actually honor the auto-upgrade.

These two issues cancelled each other out in tests (auto-upgrade was happening because [dirstate-tracked-key-v1] forced the fallback, not because of the config), which is I think why they went unnoticed earlier.