ci: migrate to centralized Plugin CI workflows

[crobibero]

TODO

• [x] add the following tokens/secrets to this repo
  • [x] JF_BOT_TOKEN - used for various tasks in the workflows (i.e. the changelog updater)
  • [x] DEPLOY_HOST - the address of the repository server (already in use for the android repos IIRC)
  • [x] DEPLOY_USER - the user that will be used to upload the release artifacts to the repository server (already in use for the android repos IIRC)
  • [x] DEPLOY_KEY - the ssh key of the user for authentications (already in use for the android repos IIRC)
• [x] disable the webhook used for the old release workflow (we don't want to release twice)

[joshuaboniface]

Org envvars should now be enabled.