Add server setting 'AdvertiseOnLocalNetwork' to be able to disable Be…

[anvilvapre]

Follow up to #21614

• No GUI changes. Optionally a checkbox could be added to the Create game server panel in future.
• Add Game.Settings.Server.AdvertiseOnLocalNetwork bool.
• Do not create a BeaconLib Beacon if set to false. Creating the Beacon already causes a UDP socket bind.

Tested, but not thourougly.

See the issue for the underlying goal.

[anvilvapre]

A setting for lanGameProbe in ServerListLogic.cs would also be needed. Or perhaps LAN could be a GameServer filter option.

[Mailaender]

Changelog