Add Nix to a new ci-image

[Anarkis]

Meanwhile doing SCA checks I found out that some repos are using Nix, and I think it's a good idea to bring it together to an image.

Repos related:

• https://github.com/rancher/terraform-aws-server/blob/main/.github/workflows/release.yaml
• https://github.com/rancher/terraform-github-rke2-download/blob/main/.github/workflows/release.yaml
• https://github.com/rancher/terraform-local-rke2-config/blob/main/.github/workflows/release.yaml
• https://github.com/rancher/terraform-null-rke2-install/blob/main/.github/workflows/release.yaml
• https://github.com/rancher/terraform-provider-rancher2/blob/main/.github/workflows/manual-rc-release.yml
• https://github.com/rancher/terraform-rancher2-aws/blob/main/.github/workflows/release.yaml