Prepare for release of HDMF 3.12.1

[rly]

Prepare for release of HDMF 3.12.1

Before merging:

• Major and minor releases: Update package versions in requirements.txt, requirements-dev.txt,
  requirements-doc.txt, requirements-opt.txt, and environment-ros3.yml to the latest versions,
  and update dependency ranges in pyproject.toml and minimums in requirements-min.txt as needed.
  Run pip install pur && pur -r requirements-dev.txt -r requirements.txt -r requirements-opt.txt
  and manually update environment-ros3.yml.
• Check legal file dates and information in Legal.txt, license.txt, README.rst, docs/source/conf.py,
  and any other locations as needed
• Update pyproject.toml as needed
• Update README.rst as needed
• Update src/hdmf/common/hdmf-common-schema submodule as needed. Check the version number and commit SHA manually
• Update changelog (set release date) in CHANGELOG.md and any other docs as needed
• Run tests locally including gallery tests, and inspect all warnings and outputs
  (pytest && python test_gallery.py)
• Run PyNWB tests locally including gallery and validation tests, and inspect all warnings and outputs
  (cd pynwb; python test.py -v > out.txt 2>&1)
• Run HDMF-Zarr tests locally including gallery and validation tests, and inspect all warnings and outputs
  (cd hdmf-zarr; pytest && python test_gallery.py)
• Test docs locally and inspect all warnings and outputs cd docs; make clean && make html
• Push changes to this PR and make sure all PRs to be included in this release have been merged
• Check that the readthedocs build for this PR succeeds (build latest to pull the new branch, then activate and
  build docs for new branch): https://readthedocs.org/projects/hdmf/builds/

After merging:

1. Create release by following steps in docs/source/make_a_release.rst or use alias git pypi-release [tag] if set up
2. After the CI bot creates the new release (wait ~10 min), update the release notes on the
   GitHub releases page with the changelog
3. Check that the readthedocs "latest" and "stable" builds run and succeed
4. Update conda-forge/hdmf-feedstock with the latest version number
   and SHA256 retrieved from PyPI > HDMF > Download Files > View hashes for the .tar.gz file. Re-render as needed

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.53%. Comparing base (232e74e) to head (aa2a9e7).
Report is 60 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1053   +/-   ##
=======================================
  Coverage   88.53%   88.53%           
=======================================
  Files          45       45           
  Lines        9603     9603           
  Branches     2731     2731           
=======================================
  Hits         8502     8502           
  Misses        778      778           
  Partials      323      323           

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