[Feature Request] Prevent fallback on initial connection

[Vagor96]

The existing config option prevent-fallback seems to only prevent fallback when the player is kicked from a server. If this is true, please consider the following feature-requests:

1. If the backend server on the initial connection is not reachable then respect prevent-fallback and immediately disconnect the player, ignoring velocity´s try list.
2. Allow configuration of affected servers by replacing the boolean prevent-fallback = false with a list format (e.g. prevent-fallback = [ ]).

Example:
The proxy has two servers configured: lobby, prison
The try-list in velocity.toml contains only one entry: lobby

1. The player´s last server is prison
2. The player disconnects
3. The player reconnects but prison is offline
4. The player gets disconnected