Prevent invalid high scores from being saved

[thomeval]

This PR adds validation to Band and Solo high scores, meaning that they will be considered invalid and thus not saved when certain conditions are met. This also includes a "Band score not saved" message on the Result screen. Unfortunately, it is not possible to filter out already existing invalid high scores, so the validation rules will only apply to scores set after this PR is merged.

Currently, a band high score will be considered invalid if the Song Speed is less than 100% :

Or if any bots are active:

It will be fairly simple to add more rules later by extending the ScoreContainer.IsSoloScoreValid() and ScoreContainer.IsBandScoreValid() methods.

Known Limitation: In some circumstances, it is possible for a Band Score to be invalid, but a player's Solo Score to still be valid (for example, when playing with bots). In such cases, we should save the player score, but not the band score. Assuming there are no blockers preventing it, this will be addressed in the Solo High Score overhaul PR.