add unittests for context menu actions

[Andreas Janz]

Concider Benjamins hints:

1. Context menu auslösen per void QWidget::contextMenuEvent(QContextMenuEvent *event)

2. erzeugtes Menü abfangen:

   1. bei DataSourceManagerTreeView via sigPopulateContextMenu = pyqtSignal(QMenu, TreeNode)
   2. bei DockManagerLayerTreeModelMenuProvider via DockManagerLayerTreeModelMenuProvider().mSignals.sigPopulateContextMenu = pyqtSignal(QMenu)

3. menu action of choice auslösen via QMenu().findChildren(QAction) <- da die gewünschte QAction

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[Andreas Janz]

Removing version: 3.10 (automated comment)

[Andreas Janz]

Not doing it.