Add automatic generation of breaks in editor

[bdach]

• Closes Break time needs to be added when editing a beatmap #14330
• Depends on Display breaks on editor timeline & allow manually adjusting their duration #28523

2024-06-19.11-53-32.mp4

Breaks are automatically inserted between objects if there is ample time to do so, namely there must be at least:

• 200ms between the last object before break and the break's start
• 650ms for the break itself
• 2 beat lengths between the break's end and the first object after break. This is a departure from stable wherein this was ruleset- and AR-dependent (by way of using preempt time), but in talking with the NAT it looked like most didn't know the specifics of how that worked so I decided I'd just use something simpler. This also probably works better for something like mania wherein the "preempt time" is largely user-settings-dependent (scroll speed).

Breaks that have been manually adjusted are not moved by the automatic regeneration on changes, unless they would break gameplay (by having an object's duration intersect a break), in which case they are forcibly removed. This manual adjustment tracking state is dodgy at best (will not work properly with undo/redo, because this info is not and should not be serialised out by the legacy beatmap encoder, which means that the manual tracking will be dropped upon undo), but it is what it is. That subsystem needs to get replaced by something else at some point anyway.

No manual add/remove of breaks right now, I'm mostly hoping we won't have to add it with this in (but will do if people request it for whatever reason I guess).

Code size is on the larger side but ~300 lines is tests so...

[peppy]

seems ok