Leverage GitHub Releases rather than tags

[haydentherapper]

Currently we cut new package releases when a tag is created. The problem is that tags can be created based on commits that are not off main, meaning they are unreviewed. #250 was an attempt at checking if the commit that tag is based on exists on main, but as discussed, there are a few issues with this approach.

@kommendorkapten and @woodruffw proposed using GitHub releases instead, which can require review from maintainers before publishing a release. We can then update the release workflows to trigger off releases:published instead of tags.