Rename livekit_server to livekit_api (#24984)

The name `livekit_server` was a bit misleading as it is not a server and
gets built into both the client and server - the server code is in
`collab`.

Release Notes:

- N/A

crates/livekit_client/examples/test_app.rs

@@ -33,7 +33,7 @@ use livekit_client::{
     AudioStream, RemoteVideoTrackView, Room, RoomEvent,
 };
 
-use livekit_server::token::{self, VideoGrant};
+use livekit_api::token::{self, VideoGrant};
 use log::LevelFilter;
 use simplelog::SimpleLogger;