Fix pre-commit workflow and other CI updates/cleanup

[altheaden]

This PR expands on some of the changes made in #136 to add some fixes and updates to various CI workflows. The changes include:

1. All static (non-matrix) versions of python used in CI have been updated to 3.13
2. PYTHON_VERSION is now defined in all workflow files for consistency
3. REVIEWERS variable is now used to list the reviewers instead of a magic string to make things more readable
4. pre_commit_update_workflow.yml has been fixed to use conda in to avoid a bug with gh which was causing permissions errors in workflow runs
5. workflow_dispatch has been added to pre_commit_update_workflow.yml CI workflow to allow manual triggering

@xylar Review checklist:

• Add @andrewdnolan as maintainer (if he isn't already)

[xylar]

@altheaden, looks great once again!