[TASK] Make the release process staged automation

[innobead]

What's the task? Please describe.

To speed up our release process in the future, we need to have an automated release flow based on git objects (tag, branch) and Github events (pre-release, release, tag). This automation is based on the current release flow first and there is no plan to change that at the beginning.

Describe the items of the task (DoD, definition of done) you'd like.

• create a release repo (longhorn/release) to manage the release process
• when creating a branch at longhorn/release, create a corresponding branch of each branch-based repos
• when creating a release tag, create a corresponding tag of each branch-based repos and update the version dependencies in the deployment-related repos (longhorn/longhorn)
• when creating a release tag, create a draft pre-release note (use https://github.com/ecatlabs/renote)
• when making a draft pre-release to release
  • release the chart (longhorn/longhorn for non-GA release, longhorn/charts for GA release) and website
  • create PRs for Rancher charts update.

Additional context

N/A

cc @meldafrawi @khushboo-rancher @kaxing