remote: Introduce a proper mock remote connection (#46337)

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/dap/src/client.rs

@@ -59,7 +59,9 @@ impl DebugAdapterClient {
 
     pub fn should_reconnect_for_ssh(&self) -> bool {
         self.transport_delegate.tcp_arguments().is_some()
-            && self.binary.command.as_deref() == Some("ssh")
+            && (self.binary.command.as_deref() == Some("ssh")
+                || (cfg!(feature = "test-support")
+                    && self.binary.command.as_deref() == Some("mock")))
     }
 
     pub async fn connect(

crates/dap/src/transport.rs

@@ -221,10 +221,7 @@ impl TransportDelegate {
             }));
         }
 
-        {
-            let mut lock = self.server_tx.lock().await;
-            *lock = Some(server_tx.clone());
-        }
+        *self.server_tx.lock().await = Some(server_tx.clone());
 
         Ok(())
     }