Rewrite Release workflow to get rid of `set-env` command

[PhilippvK]

Recent release had the following issue:

Unable to process command '::set-env name=VERSION::2.1.1.0-BETA' successfully.
---
The `set-env` command is disabled. Please upgrade to using Environment Files or opt into unsecure command execution by setting the `ACTIONS_ALLOW_UNSECURE_COMMANDS` environment variable to `true`. For more information see: https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/

Further details: https://docs.github.com/en/actions/reference/workflow-commands-for-github-actions#stopping-and-starting-workflow-commands