Move the log popup to the main window

The quiz reports point changes with an event_logged signal, and the main
window adds them to the log. Alt+L is handled by the main window.

tests/integration/test_popups.gd

@@ -3,14 +3,14 @@ extends MainWindowTestSuite
 ## dims the window behind them, and the closing click does not reach the main window.
 ## The main window and the quiz each have their own popups and their own backdrop.
 
-## Popups opened from the top bar, in the main window.
+## Popups in the main window: the ones opened from the top bar, and the log.
 const MAIN_POPUPS: Array[String] = [
-	"Search", "SyncWindow", "QRWindow", "ShortcutsWindow", "AboutWindow",
+	"Search", "SyncWindow", "QRWindow", "ShortcutsWindow", "AboutWindow", "Log",
 ]
 
 ## Popups opened from the quiz, in the Quiz scene.
 const QUIZ_POPUPS: Array[String] = [
-	"SettingsWindow", "NewCharacterSelect", "WinnerWindow", "Log",
+	"SettingsWindow", "NewCharacterSelect", "WinnerWindow",
 ]