Remove reliance on ConfigManager State on first getInstance call

[samfreund]

Not in scope for the current change set, but this is odd. This relies on ConfigManager's state when you first call getInstance, which feels like an anti-pattern to me. Can we do things more like how NetworkTablesManager works, with NetworkTablesManager.getInstance().setConfig()?

Originally posted by @mcm001 in https://github.com/PhotonVision/photonvision/pull/2171#discussion_r2595799751