953 Implement basic stochastic equation based model

[nijawa]

Changes and Information

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

• Implemented stochastic version of SIR and SIRS model, with specialized Simulations.
• Implemented Euler-Maruyama method reusing EulerIntegratorCore and a custom advance function.
• Time step dt is now updated during integration. This is currently only used by the new SDE models.
• Protected IntegratorCore for stochastic models to avoid unintended use of ODE integrators.
• Small fixes: avoid two dangling references, avoid a copy in FlowSimulation.

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

• [x] Every addressed issue is linked (use the "Closes #ISSUE" keyword below)
• [x] New code adheres to coding guidelines
• [x] No large data files have been added (files should in sum not exceed 100 KB, avoid PDFs, Word docs, etc.)
• [x] Tests are added for new functionality and a local test run was successful (with and without OpenMP)
• [x] Appropriate documentation for new functionality has been added (Doxygen in the code and Markdown files if necessary)
• [x] 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)

• [x] Corresponding issue(s) is/are linked and addressed
• [x] Code is clean of development artifacts (no deactivated or commented code lines, no debugging printouts, etc.)
• [x] Appropriate unit tests have been added, CI passes, code coverage and performance is acceptable (did not decrease)
• [x] No large data files added in the whole history of commits(files should in sum not exceed 100 KB, avoid PDFs, Word docs, etc.)
• [x] 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).

Closes #953

[reneSchm]

I double checked for dangling references. Apparently, gcc 11 and clang 17 either do not care, or more probably fix them silently (dangling references cause undefined behaviour, so the compiler is technically allowed to do anything). However, gcc 13 does complain, and in both dynamic_npis.h and mobility_io.h we used to try and assign a Range r-value to a l-value reference. That is now fixed.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 94.95413% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 96.33%. Comparing base (ce75c58) to head (baa026b).

Files	Patch %	Lines
cpp/models/sde_sir/simulation.h	86.48%	5 Missing :warning:
cpp/models/sde_sirs/simulation.h	86.48%	5 Missing :warning:
cpp/memilio/io/mobility_io.h	75.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #954 +/- ## ========================================== - Coverage 96.36% 96.33% -0.03% ========================================== Files 123 129 +6 Lines 9844 10047 +203 ========================================== + Hits 9486 9679 +193 - Misses 358 368 +10 ```

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