Add XML Export option to GUI.

[libklein]

Add XML Export option to GUI. Uses the same logic as the corresponding CLI export option. The user needs to confirm the potentially unsafe export as with the CSV export option.
Fixes #8496.

• Implemented change
• Updated documentation
• Added translations

Screenshots

TODO

The screenshot showing the export options needs to be updated.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 7.14286% with 26 lines in your changes missing coverage. Please review.

Project coverage is 64.40%. Comparing base (eaa363d) to head (eef9dba).
Report is 380 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/gui/DatabaseTabWidget.cpp	0.00%	26 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8524      +/-   ##
===========================================
- Coverage    64.41%   64.40%   -0.01%     
===========================================
  Files          339      339              
  Lines        43953    43981      +28     
===========================================
+ Hits         28309    28322      +13     
- Misses       15644    15659      +15     

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