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_api/build.rs

@@ -0,0 +1,9 @@
+fn main() {
+    prost_build::Config::new()
+        .type_attribute("SendDataResponse", "#[allow(clippy::empty_docs)]")
+        .compile_protos(
+            &["vendored/protocol/livekit_room.proto"],
+            &["vendored/protocol"],
+        )
+        .unwrap();
+}