App: Use more local methods to trigger memory trim timer

The global event filter function is executed often, for events
originating deep in the widget hierarchy even multiple times.

Triggering the timer only by mouse and key presses on the main
application and on texteditor is less intrusive and still happens
often enough (TM).

Change-Id: I848d55a347bd62d12e8523965d1750c59da33116
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/coreplugin/icore.h

@@ -124,6 +124,7 @@ public:
     static void removeContextObject(IContext *context);
 
     static void registerWindow(QWidget *window, const Context &context);
+    static void restartTrimmer();
 
     enum OpenFilesFlags {
         None = 0,