Fixes#17952.
This PR is a continuation of #20719.
It mainly involves adding `self.doc`. This new attribute is then also used in the rest of the modified classes. In some cases code was slightly reordered for consistency.
The `_finish_command_on_doc_close` function has been modifief to also handle `Gui.Snapper.ui.escape` and the code in gui_arcs.py has been updated accordingly.
Additionally:
Removed the `done` and `spacedone` variables in BimWall.py by tweaking the code.
Related: #17952.
This PR introduces a document observer to close task panels on doc close.
For now it is for the Draft Workbench only. The BIM Workbench will be dealt with in a future PR.
The basic code is simple, but to make things works some additional things were addressed:
* gui_base.py: the GuiCommandBase class was enhanced to handle App.activeDraftCommand, self.doc, self.view and self.planetracker. Strictly speaking only the first 2 are required for this PR.
* gui_base.py: self.command_name was changed to self.featureName for compatibility with gui_base_original.py. Not required for this PR.
* gui_arcs.py, gui_circulararray.py, gui_polararray.py and gui_orthoarray.py: updated in relation to the GuiCommandBase class.
* gui_arcs.py Arc_3Points: The command now has a ui property and shows a plane tracker. Only the first is required for this PR.
* gui_shapestrings.py: This command had two ui attributes: self.ui and self.task. This was problematic. To fix this the base class of the command was changed from gui_base_original.Creator to gui_base.GuiCommandBase. As a result the getStrings method is no longer available meaning that the useSupport parameter is ignored when creating a ShapeString. But since that mechanism does not work properly anyway, I feel that this is acceptable. Should many user complain the functionality can of course be reintroduced.
