Allow choosing the frame presentation mode in detail in Vulkan mode

UI/DebugOverlay.cpp

@@ -136,8 +136,9 @@ static void DrawFrameTiming(UIContext *ctx, const Bounds &bounds) {
 	ctx->BindFontTexture();
 	ctx->Draw()->SetFontScale(0.5f, 0.5f);
 
+	// NOTE: This is not necessarily the same as the actual present mode.
 	snprintf(statBuf, sizeof(statBuf),
-		"Mode (interval): %s (%d)",
+		"Timing mode (interval): %s (%d)",
 		Draw::PresentModeToString(g_frameTiming.presentMode),
 		g_frameTiming.presentInterval);