Fix core Tokio runtime panic and add network logging

- Fix tokio runtime panic by spawning a dedicated Tokio runtime thread in CoreController.
- Add central log_msg utility in src/lib.rs for debugging.
- Add instrumentation/logs to join, leave, and gossip events in src/network/gossip.rs.
- Add test_net.rs bin for testing gossip loopback sync.
- Use std::sync::Mutex in IrohGossipState to resolve Tokio block-in-async panics.

src/main.rs

@@ -1,12 +1,5 @@
-pub mod audio;
-pub mod codec;
-pub mod network;
-pub mod core;
-pub mod app;
-
-#[tokio::main]
-async fn main() {
-    if let Err(e) = app::run_gui() {
+fn main() {
+    if let Err(e) = peerspeak::app::run_gui() {
         eprintln!("Error running GUI: {:?}", e);
     }
 }