Fix ManiaModInvert permanently destroying the beatmap

[smoogipoo]

Fixes #28687

Steps to reproduce:

• Select a converted beatmap (osu! -> osu!mania).
• Select the invert mod
• Deselect the invert mod
• Select the constant speed mod.

Expected: Star rating should be equal to that of NM.
Actual: Star rating differs.

@peppy We may want a hotfix release for this (though I believe it's been broken since the mod's been introduced...).

[peppy]

@smoogipoo please take a look at 005af28. In addition to your changes, I've moved the bindable list portion to EditorBeatmap because having a bindable list replaced post-construction doesn't fill be with a lot of confidence.

[smoogipoo]

Any reason for not making it an IReadOnlyList, matching HitObjects?

[peppy]

Any reason for not making it an IReadOnlyList, matching HitObjects?

I originally did, but I believe I ran into an issue. Let me check..

[smoogipoo]

Reverted the last two commits because they're too ugly to exist, requiring the beatmap class to be reworked in general.

[smoogipoo]

lgtm.