We don't use that info for anything, and it generates unnecessary diffs
every time we bump the minor version (and CI failures if we forget to
sync some files from opt-in modules (mono, text_server_fb).
Adds a OfflineMultiplayerPeer class which behaves like a server with no
connected peers.
Use OfflineMultiplayerPeer as default for SceneMultiplayer.
This means that the SceneTree will act as the multiplayer authority by
default.
Calls to is_server will return true, and calls to get_unique_id will
return TARGET_PEER_SERVER.
