Move pipeline related files to its own folder

What does this MR do?

As part of #284894 (closed) we are restructuring the security dashboard folders. The new version has a subfolder foreach dashboard type. Previously we restructured the project, group and instance level dashboards. This commit will restructure the pipeline dashboard.

Steps to test this:

1. Fork a repository (such as https://gitlab.com/gitlab-examples/security/security-reports/)
2. Run the pipeline
3. Go to Project > CI/CD > Pipelines > Your Pipeline > Security Tab
4. Check that the pipeline displays a vulnerability list

Since the pipeline dashboard also contains a version behind a feature flag, in order to test that version as well simply enable the following feature flag: :pipeline_security_dashboard_graphql

Screenshots (strongly suggested)

There are no visual changes but here's a screenshot that confirms it's still working:

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• 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 #284894 (closed)