Banner to notify and gather feedback on needs view in pipeline

What does this MR do?

Adds a banner inside the pipeline view if the user is using pipeline_graph_layers_view feature flag that tell the user about this new feature. The banner has a link to the needs doc and a CTA that leads to a feedback issue. Once it has been dismissed, we call the graphQl mutation for createUserCallout which makes sure the user will never see this notification again.

Since this feature will be short lived, the tests and code in general have been made specifically for this usecase and is not created to scale or change later. I have written some basic tests just to make sure this is working, but nothin fancy 😄

Screenshots (strongly suggested)

Screen_Recording_2021-04-14_at_12.11.39_PM

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this is behind a disabled feature flag.
• [-] 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

Related to #322014 (closed)