Add option for lazy creation of micro simulations

[mathiskelm]

Micro simulations that are never solved don't require the microsim object to be created in the first place. If the creation/initialization is costly, avoiding it can save significant time/memory and allow simulation on smaller systems/of larger problems. In this PR the creation of micro simulations is delayed to activation.

TODO:

• Avoid code duplication for creation of micro sims,
• Improve compatibility with other Micro-Manager capabilities such as initialization of micro-sims.
• Improve error handling of incompatible settings (without initial macro data the simulation will start with only 1 micro sim)

Checklist:

• I made sure that the CI passed before I ask for a review.
• I added a summary of the changes (compared to the last release) in the CHANGELOG.md.
• If necessary, I made changes to the documentation and/or added new content.
• I will remember to squash-and-merge, providing a useful summary of the changes of this PR.