Publish chart & image to private GitHub registry

[richardcase]

What would you like to be added (User Story)?

As a developer
I want the Rancher Turtles chart published to a private registry that is easily accesible
So that they can be used for testing

Detailed Description

We will publish the chart and images to 2 places:

1. Rancher Prime Registry (Publish chart & images to Rancher Prime registry  #81)
2. Private GHCR (this issue)

Anything else you would like to add?

No response

Label(s) to be applied

/kind feature

[furkatgofurov7]

Some more notes after offline discussion:

• Rancher Prime Registry Publish chart & images to Rancher Prime registry  #81: update the default image in the chart values yam to point to the prime registry. Update the release workflow to tag and push the image to the prime registry.
• Private GHCR (this issue): we will be re-using the same GHA we currently have since we are publishing charts in the github pages and images in ghcr
• (new): add nightly builds to publish charts and images in ghcr and make sure they are private: ✨ Add nightly chart and image publish GH workflow #135

[furkatgofurov7]

All relevant PRs are merged, @richardcase can this be closed now?