Remove sorting on attrdict key nesting

[brynpickering]

Fixes #576

Summary of changes in this pull request:

• Remove sorting on key nesting
• Add test
• Snuck in some missing changelog entries

Reviewer checklist:

• [ ] Test(s) added to cover contribution
• [ ] Documentation updated
• [ ] Changelog updated
• [ ] Coverage maintained or improved

[codecov[bot]]

Codecov Report

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

Project coverage is 95.86%. Comparing base (872978d) to head (6af8eb0). Report is 3 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #578 +/- ## ========================================== + Coverage 95.85% 95.86% +0.01% ========================================== Files 24 24 Lines 3619 3629 +10 Branches 788 724 -64 ========================================== + Hits 3469 3479 +10 Misses 86 86 Partials 64 64 ``` | [Files](https://app.codecov.io/gh/calliope-project/calliope/pull/578?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=calliope-project) | Coverage Δ | | |---|---|---| | [src/calliope/attrdict.py](https://app.codecov.io/gh/calliope-project/calliope/pull/578?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=calliope-project#diff-c3JjL2NhbGxpb3BlL2F0dHJkaWN0LnB5) | `96.51% <100.00%> (ø)` | |