Add support for ruleset-specific blueprints in editor timeline

[OliBomby]

RFC. This PR allows rulesets to customize how hit objects are represented in the timeline without having to modify the hit object classes or create additional interfaces.
The need for this has been expressed multiple times already in #29441 and #21566

The API is a bit limited because it expects objects of type TimelineHitObjectBlueprint which already defines all the layout and interactions. If more freedom is required, I think TimelineHitObjectBlueprint should not define layout and instead the parts of it should be split into separate classes which could be composited instead.

As an example I've implemented two ruleset-specific changes that make use of this API:

• Sample points at the tail end of spinners
• Disabled timeline in mania (as in stable)

The IHasDisplayColour interface can also be eliminated in favour of taiko specific timeline blueprints.

[bdach]

If we're going to go and say that it's fine for the timeline to look differently on different rulesets, then I can already tell you that this API is too constrained and we'll need a higher-level primitive anyway to replace the entirety of the timeline.

Why, you ask? One of the most frequent pieces of feedback on scrolling rulesets (taiko and mania) are that scroll speed changes should be visible on the timeline. And osu!'s displays above hitobjects do not make sense there because that's not how speed changes work on those rulesets - they affect the entire playfield. So they should probably look closer to the red timing change markers.

So I think this sort of thing is too short-sighted and we'll have to tear it out sooner than later anyway. Not opposed to the idea, yet wholly opposed to this execution.

[bdach]

The above comment notwithstanding I'm gonna need @peppy cross-check on this, since I vividly remember him being vehemently opposed to the notion of per-ruleset deviations of any sort on the timeline, although I cannot find the paper trail for this. I think it must have been somewhere around when we started to implement this editor design. I think it could have been in stream twitch chat or something...?