`set-output` workflow commands are being deprecated

[adpaco-aws]

Proposed change: Replace set-output workflow commands with environment files.

Motivation: GitHub is deprecating save-state and set-output workflow commands. More details can be found here. A warning about this deprecation is appearing in our workflows (see this Release worfklow for example).

[adpaco-aws]

There is a single set-output instance in our release workflow, but the action run which includes the proposed fix continues to warn about set-output. If I'm not mistaken, they come from the Create release step which is using actions/create-release@v1, but that action is unmaintained and deprecated.

Therefore, we should consider switching to a different action. This one is maintained and offers a wide variety of features.