Remove duplicate queries object and move it to dashboard panels object

What does this MR do?

As part of the an effort to ensure compatibility from different data sources, the dashboard "normalized" data to ensure data will always available.

Now that the compatibility is not needed thanks to !15709 (merged), the data sources are uniform again.

Objects in dashboard store have been renamed from

• dashboard[].metrics to dashboard[].panels
• panel[].queries to panel[].metrics

Other components that depend in this data have been updated.

Screenshots

N/A

Checked features

• Metrics Dashboard
• Embed markdown
• Cluster Health

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

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

Relates to #31565 (closed) and supports efforts on #34121 (closed)