feat(admin-only-build-option)

[zolantris]

• per user request on Discord, I add an option to hide hammer menu items registered under ValheimRAFT for clients that are not admins.
• update prefab registry to safely set netview.
• update prefab registry to disable pieceManager items registered for valheimRAFT if the AdminsCanOnlyBuildRaft is set to true on a server. On singleplayer this will always still allow building raft items
• add listeners for server admin status changes to update hammer menu.
• add listeners for when server config syncs to attempt to enable/disable the prefabs again. This allows toggling the AdminsCanOnlyBuildRaft flag which will enable building for all users
• AdminsCanOnlyBuild is set to false by default