libcamera: Don't use emitter object pointer argument to slot

In many cases, the emitter object passed as a pointer from signals to
slots is also available as a class member. Use the class member when
this occurs, to prepare for removal of the emitter object pointer from
signals.

In test/event.cpp, this additionally requires moving the EventNotifier
to a class member.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>

utils/ipc/generators/libcamera_templates/module_ipa_proxy_worker.cpp.tmpl

@@ -57,10 +57,10 @@ public:
 
 	~{{proxy_worker_name}}() {}
 
-	void readyRead(IPCUnixSocket *socket)
+	void readyRead([[maybe_unused]] IPCUnixSocket *socket)
 	{
 		IPCUnixSocket::Payload _message;
-		int _retRecv = socket->receive(&_message);
+		int _retRecv = socket_.receive(&_message);
 		if (_retRecv) {
 			LOG({{proxy_worker_name}}, Error)
 				<< "Receive message failed: " << _retRecv;