[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: rancher/charts#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.\

• 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:

• Validate release charts charts-build-scripts#149

PRs on charts side:

• [release-v2.9] Charts release validation charts#4424
• [release-v2.8] Charts release validation 2.8 charts#4427
• [release-v2.10] Charts release validation 2.10 charts#4428

[nicholasSUSE]

Holding this task for now in favor of: #475