fix: don't detach threads (#6333)

Previously, we would detach threads that did not exit in a reasonable
time, meaning they'd continue running and potentially accessing data
that had been freed, causing us to crash.
With this change, we _dont_ detach the thread, and let the thread
destructor do as it pleases (which will be terminating).
Neither solution is clean - old solution would sometimes work, but this
should give us a better indicator of where we're doing things wrong.

src/controllers/sound/MiniaudioBackend.cpp

@@ -235,7 +235,6 @@ MiniaudioBackend::~MiniaudioBackend()
 
         qCWarning(chatterinoSound)
             << "Audio thread did not stop within 1 second";
-        this->audioThread->detach();
     }
 }
 

src/providers/liveupdates/BasicPubSubManager.hpp

@@ -175,9 +175,7 @@ public:
         }
 
         qCWarning(chatterinoLiveupdates)
-            << "Thread didn't finish after stopping, discard it";
-        // detach the thread so the destructor doesn't attempt any joining
-        this->mainThread_->detach();
+            << "Thread didn't finish after stopping";
     }
 
 protected:

src/providers/twitch/PubSubManager.cpp

@@ -143,10 +143,7 @@ void PubSub::stop()
         return;
     }
 
-    qCWarning(chatterinoLiveupdates)
-        << "Thread didn't finish after stopping, discard it";
-    // detach the thread so the destructor doesn't attempt any joining
-    this->thread->detach();
+    qCWarning(chatterinoLiveupdates) << "Thread didn't finish after stopping";
 }
 
 void PubSub::listenToChannelPointRewards(const QString &channelID)