Release workflows & cleanup

[kbonney]

Summary

The goal of this PR is to streamline release automation and workflow layout (PyPI + conda-forge, clearer file names).

• The building and testing of wheels has been extracted into its own file build_test_wheels.yml. Runs on merges to main, rather than on every commit to a PR.
• The releasing to PyPI has been extracted to its own file publish_pypi.yml. This is triggered on tags and uses build_test_wheels.yml to prepare the wheels to be published.
• A new workflow for releasing to conda-forge has been added in publish_conda.yml. This is manually triggered and takes the release version name as an input. It handles updating meta.yml and preparing the PR to wntr-feedstock.
• What was previously called build_tests.yml is now called test_repository.yml and only handles running tests/coverage on installations directly from the repository. This runs on every PR and is the remains the primary indicator for repository health.
• For consistency and clarity across the multiple workflow files, a standard naming convention for filenames, workflow name fields, and job name files has been applied. This should increase readability of the reports on the Actions tab. Relevant links in the README and documentation have been updated to account for these changes.

Tests and documentation

New features require tests and documentation.

Acknowledgement

By contributing to this software project, I acknowledge that I have reviewed the software quality assurance guidelines and that my contributions are submitted under the Revised BSD License.