Connect densities rebase of PR #619

[Andrea-Havron-NOAA]

What is the feature?

• This PR addresses issue [Refactor]: Edit connections between fleet.hpp and distributions #586 and is a rebase of PR Connect densities #619

How have you implemented the solution?

The fleet.hpp file was edited to depend on the new density classes. The interface and tests were modified to accomodate changes.

Does the PR impact any other area of the project?

This change does not affect input or output

How to test this change

test_rcpp_tmb_distributions and test-integration-fims-estimation

Developer pre-PR checklist

• I relied on GitHub actions to 🧪 things for me while I sat on the 🛋️.

[github-actions]

Instructions for code reviewer

Hello reviewer, thanks for taking the time to review this PR!

• Please use this checklist during your review, checking off items that you have verified are complete!
• For PRs that don't make changes to code (e.g., changes to README.md or Github actions workflows), feel free to skip over items on the checklist that are not relevant. Remember it is still important to do a thorough review.
• Then, comment on the pull request with your review indicating where you have questions or changes need to be made before merging.
• Remember to review every line of code you’ve been asked to review, look at the context, make sure you’re improving code health, and compliment developers on good things that they do.
• PR reviews are a great way to learn, so feel free to share your tips and tricks. However, for optional changes (i.e., not required for merging), please include nit: (for nitpicking) before making the suggestion. For example, nit: I prefer using a data.frame() instead of a matrix because...
• Engage with the developer when they respond to comments and check off additional boxes as they become complete so the PR can be merged in when all the tasks are fulfilled. Make it clear when this has been reached by commenting on the PR with something like This PR is now ready to be merged, no changes needed.

Checklist

• The PR is requested to be merged into the appropriate branch (typically main)
• The code is well-designed.
• The functionality is good for the users of the code.
• Any User Interface changes are sensible and look good.
• The code isn’t more complex than it needs to be.
• Code coverage remains high, indicating the new code is tested.
• The developer used clear names for everything.
• Comments are clear and useful, and mostly explain why instead of what.
• Code is appropriately documented (doxygen and roxygen).