Update deprecated github actions

[melange396]

Deprecation warnings have shown up in various github actions summaries recently (such as https://github.com/cmu-delphi/delphi-epidata/actions/runs/7628606640 and https://github.com/cmu-delphi/delphi-epidata/actions/runs/7628606653) :

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2, actions/setup-node@v2, actions/cache@v2, actions/setup-python@v2, actions/upload-artifact@v2, AButler/upload-release-assets@v2.0, docker/login-action@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

[we may be using more of these deprecated actions that i didnt come across]

The `save-state` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

[same for `set-output`, if that wasn't already obvious]

Input 'packages_dir' has been deprecated with message: The inputs have been normalized to use kebab-case. Use packages-dir instead.

[same for 'skip_existing' / `skip-existing` and possibly others as well]

The priority for these changes is probably fairly low, as the are successfully running in some sort of compatibility mode, but nevertheless we should migrate them as they are not expected to continue to work indefinitely.

[melange396]

set-output is covered by #1015