1242 update simple surrogate model

[mhheger]

Changes and Information

Please briefly list the changes (main added features, changed items, or corrected bugs) made:

• restructuring the existing code for simple surrogate models
• adding tests

If need be, add additional information and what the reviewer should look out for in particular:

Merge Request - Guideline Checklist

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Checks by code author

• Every addressed issue is linked (use the "Closes #ISSUE" keyword below)
• New code adheres to coding guidelines
• No large data files have been added (files should in sum not exceed 100 KB, avoid PDFs, Word docs, etc.)
• Tests are added for new functionality and a local test run was successful (with and without OpenMP)
• Appropriate documentation for new functionality has been added (Doxygen in the code and Markdown files if necessary)
• Proper attention to licenses, especially no new third-party software with conflicting license has been added
• (For ABM development) Checked benchmark results and ran and posted a local test above from before and after development to ensure performance is monitored.

Checks by code reviewer(s)

• Corresponding issue(s) is/are linked and addressed
• Code is clean of development artifacts (no deactivated or commented code lines, no debugging printouts, etc.)
• Appropriate unit tests have been added, CI passes, code coverage and performance is acceptable (did not decrease)
• No large data files added in the whole history of commits(files should in sum not exceed 100 KB, avoid PDFs, Word docs, etc.)
• On merge, add 2-5 lines with the changes (main added features, changed items, or corrected bugs) to the merge-commit-message. This can be taken from the briefly-list-the-changes above (best case) or the separate commit messages (worst case).

[HenrZu]

i had a first brief look at most of the secir_simple functions. Lets discuss the points before you start working on this :) Looks really good, great work :)

[HenrZu]

great work :) Some more comments. Regarding the ones about the secir groups. We can skip them and adress them in the next pull request since we only wanted to deal with the secir simple one and still need to rework the groups one.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.21%. Comparing base (12b041d) to head (a3ef9e2).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1252      +/-   ##
==========================================
- Coverage   97.23%   97.21%   -0.03%     
==========================================
  Files         155      167      +12     
  Lines       14278    14960     +682     
==========================================
+ Hits        13883    14543     +660     
- Misses        395      417      +22     

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[HenrZu]

This also closes #849