893 add initialization method with real data for lct model

[lenaploetzke]

Changes and Information

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

• added ConfirmedCasesNoAgeEntry to epi_data

• added method to use real data for an initialization of the lct model - method is comparable to the initialization of the ODE model, see also the master thesis

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

• Do you think an example should be added here? I would possibly suggest a shared example with the second initialization method (see #897).

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
• [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
• [ ] 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).

Closes #893

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.29%. Comparing base (f005eaf) to head (7b1b461).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #920 +/- ## ========================================== + Coverage 96.21% 96.29% +0.07% ========================================== Files 122 123 +1 Lines 9638 9844 +206 ========================================== + Hits 9273 9479 +206 Misses 365 365 ```

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[lenaploetzke]

I have to restructure the file parameters_io.h because of the extensive changes of the LCT model in the main branch. The functionality will remain the same.