CA-Chart Readme Updates & Fix Chart Lint and Test Actions

[gjtempleton]

• Fixes What is the correct chart version ? #3899 by clarifying Helm chart versioning confusion, hides details under an expandable section and makes strong recommendation to use supported version
• Updates the image for the repo to point at the raw kubernetes logo, for Artifact hub purposes, the current URL 404s
• Updates the default Cluster-autoscaler image repository to the full vanity URL rather than the US endpoint, this should provide some speed benefits for non US based users
• Fixes the helm testing and linting actions run on PRs, as per discussion on a previous PR this should have been caught by the action but due to the major version bump in the GH actions not also changing the invoking of the actions as per the Action's docs, they hadn't been successfully running, instead failing silently upon installing the actions. Tested as failing PRs which do not bump the chart version on my fork.

[mwielgus]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gjtempleton, mwielgus

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [mwielgus]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment