Testing Framework and initial tests

[mpatrou]

It includes the testing framework, initial tests, ruff code D and docstrings, and some other improvements

Short description of the changes:

It includes:

• pytest configurations and fixtures
• initial tests for main window, application start, version, configuration settings
• argument parsing
• ruff code D added for dosctrings
• docstrings in classes, tests and files added
• init update for importing in Mantid workbench
• HyspecPlanningTool class changes in _new_ ()

Long description of the changes:

Check list for the pull request

• I have read the [CONTRIBUTING]
• I have read the [CODE_OF_CONDUCT]
• I have added tests for my changes
• I have updated the documentation accordingly

Check list for the reviewer

• I have read the [CONTRIBUTING]
• I have verified the proposed changes
• best software practices
  • all internal functions have an underbar, as is python standard
  • clearly named variables (better to be verbose in variable names)
  • code comments explaining the intent of code blocks
• All the tests are passing
• The documentation is up to date
• code comments added when explaining intent

Manual test for the reviewer

References

[Story][PPT] Include initial tests in the code base

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.50%. Comparing base (1978169) to head (ecbc044).

Additional details and impacted files

@@            Coverage Diff             @@
##            next       #2       +/-   ##
==========================================
+ Coverage   1.60%   90.50%   +88.90%     
==========================================
  Files          4        8        +4     
  Lines        125      158       +33     
==========================================
+ Hits           2      143      +141     
+ Misses       123       15      -108     

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