[qt_common, core, audio] remove duplicate string literal definitions, inline SystemManager::threadfunc, increase latency of audio shutdown (#3030)

Very small code cleanup, also remove `[[unlikely]]` because it doesn't matter + increase latency of audio render when shutting down

Signed-off-by: lizzie lizzie@eden-emu.dev

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3030
Reviewed-by: Caio Oliveira <caiooliveirafarias0@gmail.com>
Reviewed-by: crueter <crueter@eden-emu.dev>
Co-authored-by: lizzie <lizzie@eden-emu.dev>
Co-committed-by: lizzie <lizzie@eden-emu.dev>

src/video_core/fence_manager.h

@@ -227,9 +227,7 @@ private:
     }
 
     void ReleaseThreadFunc(std::stop_token stop_token) {
-        std::string name = "GPUFencingThread";
-
-        Common::SetCurrentThreadName(name.c_str());
+        Common::SetCurrentThreadName("GPUFencingThread");
         Common::SetCurrentThreadPriority(Common::ThreadPriority::High);
 
         TFence current_fence;