Fix converted beatmap hitwindows not working correctly

[smoogipoo]

There were two issues:

1. Hit windows were correct when the ruleset matched the beatmap's ruleset, i.e. mania beatmap with mania ruleset. But hit windows were not correct when the rulesets didn't match - mania would use osu!'s hit windows.
2. Because hit windows were passed from the convert hitobjects, which are retained for the same working beatmap, mania could mangle the hit windows and add lenience / allow-oks / allow-perfects, and osu! would next time use those same mangled hit windows.