Add a Secure E2E test for pipeline reports

What does this MR do?

Adds an end-to-end test that executes a pipeline and validates that security reports appear in the pipeline display.

Establishes a new fixture that contains a repository that will skip scanner execution and upload a pre-generated report artifact.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

Related to #9192 (moved)

Element definition to support this MR was added in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/28416