Came across an issue where `LeaderboardScoreTooltip` attempts to capitalize all letters for the `displayName`.
Unsure if I should completely ignore it and localise it anyway.
Also, remove nullable disable annotation for all using classes.
Setting store can be nullable because `RulesetConfigManager()` can accept null setting store.
- make `UserActivity.InGame` and derive that to `InSoloGame` and `InMultiplayerGame`
- rename `SoloGame` to `InSoloGame`
- rename `MultiplayerGame` to `InMultiplayerGame`