Release PR for PyNWB 4.0.0.

Minor changes:

ROS3 CI fix: The *-ros3 jobs failed with OSError: ... AWS region wasn't specified. Root cause is environment drift: HDF5 2.1.0 / h5py 3.16.0 (released between the last green dev run and this run) now require an explicit AWS region for the ROS3 driver. Fixed by passing aws_region="us-east-2" (DANDI Archive bucket region) at each ROS3 open site and adding an aws_region argument to validate().

Overlap with #2187 (Zarr validation): The aws_region addition here touches validate() / _validate_single_file / get_cached_namespaces_to_validate — the same code that #2187 refactors. However, I would like to pursue a different approach with regard to validate / get_cached_namespaces_to_validate that needs to propagate through major versions of HDMF and PyNWB. For now, this change forwards aws_region alongside the existing driver kwarg. validate() on a Zarr store remains broken on this branch (pre-existing).

Before merging:

• Make sure all PRs to be included in this release have been merged to dev.
• 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. _{Done via pur; requirements.txt/requirements-dev.txt were already current. numpy/pandas kept within hdmf and pandas<3 ceilings. requirements-min.txt and pyproject.toml ranges left unchanged (no change needed). Not yet validated by the test/CI steps below.}
• Check legal file dates and information in Legal.txt, license.txt, README.rst, docs/source/conf.py,
  and any other locations as needed _{Copyright year updated 2017-2025 → 2017-2026.}
• Update pyproject.toml as needed _{No change needed; version is derived dynamically from the git tag.}
• Update README.rst as needed _{Copyright year updated.}
• Update src/pynwb/nwb-schema submodule as needed. Check the version number and commit SHA
  manually. Make sure we are using the latest release and not the latest commit on the main branch. _{Already at the 2.10.0 release tag.}
• Update changelog (set release date) in CHANGELOG.md and any other docs as needed _{Left as (Upcoming) until the release date is known.}
• Run tests locally including gallery, validation, and streaming tests, and inspect all warnings and outputs
  (python test.py -v -p -i -b -w -r > out.txt 2>&1). Try to remove all warnings.
• Test docs locally and inspect all warnings and outputs cd docs; make clean && make html
• After pushing this branch to GitHub, manually trigger the "Run all tests" GitHub Actions workflow on this
  branch by going to https://github.com/NeurodataWithoutBorders/pynwb/actions/workflows/run_all_tests.yml, selecting
  "Run workflow" on the right, selecting this branch, and clicking "Run workflow". Make sure all tests pass.
  • https://github.com/NeurodataWithoutBorders/pynwb/actions/runs/28409545413
• Check that the readthedocs build for this PR succeeds (see the PR check)

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 "stable" build runs and succeeds
4. Either monitor conda-forge/pynwb-feedstock for the
   regro-cf-autotick-bot bot to create a PR updating the version of HDMF to the latest PyPI release, usually within
   24 hours of release, or manually create a PR updating recipe/meta.yaml with the latest version number
   and SHA256 retrieved from PyPI > PyNWB > Download Files > View hashes for the .tar.gz file. Re-render and update
   dependencies as needed.

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