It is an expectation of users that when the HUD is shown after a period
of being hidden, it will visually reflect the state based on recent
judgements.
To achieve this, I've added `AlwaysPresent` and moved the transform
application to the meter level, rather than at a child level. If this is
seen as a bad direction, `AlwaysPresent` can be applied to the drawable
children and the transforms can be moved back.
Also of note, `ColourHitErrorMeter` is pretty weird. The flow class
could potentially be removed and reduce `AlwaysPresent` usage by one.
Can do that refactor as part of this PR if preferred.
Closes#18624.
+ Stopped using testing methods in non-testing classes
+ Resolve Player and add OnSeek event
+ Take bindings away from BarHitErrorMeter
+ Add support for ColourHitErrorMeter
It's not valid in the base `HitErrorMeter`, as the colour meter only
displays colour for a given judgement, so it is still valid to add new
items to it even if the hit window is 0, as misses are still possible.
