Add Banzai Filter for Cluster Metrics

What does this MR do?

Overview

Part of the work to embed cluster health metrics charts in an issue description (or any other notable) by adding a url to the chart in the Gitlab Flavored Markdown of the Issue description field.

Technical Details

Adds a banzai filter for cluster metrics which inserts a div into the issue description with the metric_dashboard url for clusters that can be queried on the front end to get access to the prometheus chart data. Note: the embedded version of the cluster metrics_dashboard_url is not yet created/merge.

This appended div will redacted based on the class name on the div since we have not changed the permissions in permissions_by_route.

Because the embedded metrics_dashboard endpoint is not yet implemented this MR intentionally leaves the div redacted for all users. Thus the MR is backstage.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team