Add rate adjustment settings for all time mods (DT/HT/NC/DC/WU/WD)

[peppy]

Resolves #7162.

• Depends on Add per-mod settings #6432.
• Depends on Fix track rate not correctly accounting for aggregates osu-framework#3095.
• Depends on Add tempo adjustment support osu-framework#3087.
• Depends on Move available mods to global context #7172.

[huoyaoyuan]

How would these mods be ranked/scored then? It makes sense to be ranked only at default rate, but that requires some more mechanism.

[peppy]

No idea. Ranking is not a consideration yet.

[peppy]

Test failure fixed in ppy/osu-framework#3095

[smoogipoo]

👍

[smoogipoo]

One thing I noticed is that if you enable DT then exit song select and go back in, the customise button will be greyed out.

[peppy]

Once #7172 is merged, I will rebase this PR, removing the #7170 commits and using #7172 logic instead.

[l3lackShark]

I encountered 2 bugs with this branch.

1. Approach circle of the first note makes "jumps" in speed when the speed multiplier is applied.
2. Several beatmaps crash on transition to gameplay, including this one: https://osu.ppy.sh/beatmapsets/659007#osu/1768802

Spoiler

2019-12-13 00:13:16: Unhandled exception has been allowed with 0 more allowable exceptions .
2019-12-13 00:13:16: An unhandled error has occurred.
2019-12-13 00:13:16: System.ArgumentNullException: Value cannot be null.
2019-12-13 00:13:16: at System.Threading.Monitor.ReliableEnter(Object obj, Boolean& lockTaken)
2019-12-13 00:13:16: at osu.Framework.Graphics.Drawable.dispose(Boolean isDisposing)
2019-12-13 00:13:16: at osu.Framework.Graphics.Drawable.Finalize()

[peppy]

@l3lackShark the second (crash) bug has been fixed via dependent PRs. The jump in speed may still exist, but can be addressed elsewhere. after this is merged into master, please open an issue if it still occurs!