Cluster Embed Metric Dashboard Endpoint

What does this MR do?

This provides an endpoint that returns data for cluster metrics filtered to 1 panel that matches the title, group and y_label given in the query_params. This allows a gitlab chart to unfurl in a Notable field that supports Gitlab Flavored Markdown.

This is the final part of: #40997 (closed)

Technical Overview

Inherits from the DynamicEmbedService to take advantage of filtering.

Screenshots

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