Use trusted publishing on PyPI

[HGSilveri]

• Changes the publish.yml workflow to use a Trusted Publisher instead of a token (thus avoiding storing tokens as secrets)
• Replaces twine with the official PyPI Publish Github Action
• Adds a release Github environment to better manage the release process

The changes were tested through a dummy deployment to TestPyPI and then replicated for the PyPI case (without a dummy deployment so as to not pollute the official repo).