Feature/parallel in time optimization

Issue/feature addressed

Optimization was disable for Parallel-in-Time simulation. This MR provide a full implementation of optimization for Parallel-in-Time support.

Proposed solution

Update CollectionOptimization to independently optimizing for each time level. This is achieved by using a map of a map with the time level as a key parameter. If a time level is missing from the optfile, then only the missing time level will be updated.

Implementation

A more detailed description of the changes. Please include any details necessary for reviewers to understand your work, and point out particular points would like them to pay particular attention to.

Tests

Suggested reviewers

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Notes

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Checklist

• Functions and classes, or changes to them, are documented.
• [ ] User guide/documentation is updated.
• Changelog is updated.
• [ ] Suitable tests added for new functionality.
• Contributed code is correctly formatted. (See the contributing guidelines).
• [ ] License added to any new files.
• No extraneous files have been added (e.g. compiler output or test data files).