Add Total rendering metrics to Performance Bar

What does this MR do?

Adds total rendering metrics including FE timings:

• BE = Time that the actual page to come to the browser
• FCP = First Contentful Paint
• DOM = DomContentLoaded Event
• Number of Requests that the page fired
• In the details is a list of all resources that were loaded by the page, their size and the duration

Next step will be adding warnings around Frontend topics (For example avatars loaded not from the CDN, huge requests, etc.)

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

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