Make application structure loading dynamic

[Citymonstret]

All application structure implementations (currently sqlite, mongo and mysql) required hard-coded switch brances (https://github.com/Sauilitired/Kvantum/blob/b6ed56bcfafd0b38f837ec1a300c2d7b595b0ca9/Implementation/src/main/java/xyz/kvantum/server/implementation/SimpleServer.java#L286) which should not be the case. This makes it hard to expand upon this, and there's also no reason why the application structure options should be limited to the internal (standalone) application structure.