[charts] Implement Chart Release Validations on GHActions

[nicholasSUSE]

When making Pull Requests for releasing charts against the release-v2.* branches, 3 Checkpoints must be manually reviewed.

Example: https://github.com/rancher/charts/pull/4369

Task

Implement all these Checkpoints on GHActions jobs.

The jobs must call Golang code from charts-build-scripts if needed.

Separate the 3 checks into 3 Pull Request, each one is very complex.\

• [x] Checkpoint 0: Validate release.yaml
• [ ] Checkpoint 1: Compare contents of assets/ to charts/
• [ ] Checkpoint 2: Compare assets against index.yaml

[nicholasSUSE]

Charts-build-scripts implementation:

• https://github.com/rancher/charts-build-scripts/pull/149

PRs on charts side:

• https://github.com/rancher/charts/pull/4424
• https://github.com/rancher/charts/pull/4427
• https://github.com/rancher/charts/pull/4428

[nicholasSUSE]

Holding this task for now in favor of: https://github.com/rancher/ecm-distro-tools/issues/475