[a.fixFabio] PyInterpreter: fx Python memory management regarding new and borrowed references; improve error messaging (Closes #1063 and #1070)

Merging branch 'a.fixFabio'  into 'main'.

See merge request !2839

Merging branch 'm.0'  into 'main'.

See merge request !2841

Merging branch 'j.2'  into 'main'.

See merge request !2840

The error message reporting and traceback is corrected and improved.
The full error report is displayed in the GUI and sent to stderr.

Example (stderr):
```
---PyInterpreter: Error:
PyInterpreter:BornAgain: Failed executing Python function 'get_sample'
------------------------------
* Python exception:
No module named 'noneexistantpackage'

Traceback (most recent call last):

  File "<string>", line 6, in get_sample

ModuleNotFoundError: No module named 'noneexistantpackage'

------------------------------
* Runtime environment:
------------------------------
```

Resolves issue #1063

Note that Python's borrowed references must _not_ be decremented by 'Py_DECREF' after use.

The 'borrowed' Python reference obtained via 'PyDict_GetItemString' and
'PyModule_GetDict' was incorrectly decremented by 'Py_DECREF', leading to a
memory access violation.

Resolve issue #1070

Merging branch 'j.1'  into 'main'.

See merge request !2837

Merging branch 'j.0'  into 'main'.

See merge request !2836

[j.0] change default values for use_average_materials and include_specular_peak; replace radio buttons by check box; change text and add tooltip to explain use_average_materials (#1061) (Closes #1061)

Merging branch 'j.0'  into 'main'.

See merge request !2832

Merging branch 'j.2'  into 'main'.

See merge request !2835

Merging branch 'j.2'  into 'main'.

See merge request !2834

Merging branch 'j.2'  into 'main'.

See merge request !2833

Merging branch 'j.0'  into 'main'.

See merge request !2831

Merging branch 'j.0'  into 'main'.

See merge request !2830