UI: Remove OBSContext class and shutdown in run_program

The OBSContext never called obs_startup but would always call
obs_shutdown in its destructor, resulting in shutdown calls even if
libobs wasn't initialized (eg due to a startup error). Instead, we now
track if libobs was initialized in OBSApp and call shutdown in the
destructor.

UI/obs-app.hpp

@@ -72,10 +72,11 @@ private:
 	std::string theme;
 	ConfigFile globalConfig;
 	TextLookup textLookup;
-	OBSContext obsContext;
 	QPointer<OBSMainWindow> mainWindow;
 	profiler_name_store_t *profilerNameStore = nullptr;
 
+	bool libobs_initialized = false;
+
 	os_inhibit_t *sleepInhibitor = nullptr;
 	int sleepInhibitRefs = 0;