Issue #400: Rename to naive model and latent model

[athowes]

Description

This PR closes #400. As agreed it replaces:

• direct_model with naive_model
• latent_individual with latent_model

I used find and replace to make sure there are no instances of "individual" or "direct" left.

This also needs me to make the change from "cohort" to "marginal" over at #221 which I'll do now.

Checklist

• My PR is based on a package issue and I have explicitly linked it.
• I have included the target issue or issues in the PR title in the for Issue(s) issue-numbers: PR title
• I have read the contribution guidelines.
• I have tested my changes locally.
• I have added or updated unit tests where necessary.
• I have updated the documentation if required.
• My code follows the established coding standards.
• I have added a news item linked to this PR.
• I have reviewed CI checks for this PR and addressed them as far as I am able.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.17%. Comparing base (d02c7c7) to head (bc00fd4).
Report is 50 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #433      +/-   ##
==========================================
+ Coverage   88.55%   94.17%   +5.61%     
==========================================
  Files          11       16       +5     
  Lines         402      429      +27     
==========================================
+ Hits          356      404      +48     
+ Misses         46       25      -21     

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[seabbs]

Sorry about this but duplicate work is in #441 so I think we should close this

[athowes]

Hi @seabbs, I'm a bit confused/upset about you closing this.

We agreed about doing the work in this PR. This was already finished before #441. The work in #441 was not part of what we agreed to work on this week, and does not have an issue, or anyone else's input.

I am waiting on this name change implemented by #433 to rebase other PRs that we agreed to work on this week. So this not being merged is slowing me down on doing the work we need to do to finish up the existing issues we agreed to work on.

As general principle, PRs should be scoped out and modular rather than bundled in together. Work should be agreed upon and executed, rather than unilaterally decided. These are the (good) principles that you've taught me!

I'd prefer that we merged this existing PR. If there is duplicate work in #441 (as I say, which was done after this was already complete), then it'll be an easy rebase. I don't understand why not merge this and then rebase #441 with it merged in the first instance?

[seabbs]

Sorry for the crossed wires Adam and you are right it would be better to have PRs be based on scoped out issues.

[athowes]

Too much work to rebase, closing again.