Makes it hard to test anything because `EditorBeatmap`'s `Update` method
updates whether a beatmap has timing or not (enabling the placement
controls).
Also adds a basic timing point to allow for better testing.
Alternate method is to expose a `SnapDistancesChanged` event in
`IPositionSnapProvider` instead, but I chose this way as an analogue to
`IBeatSnapProvider.BeatDivisor`, which might even make sense to be
exposed as `BindableBeatDivisor` instead of caching that separately.