workflow:rules Configuration for Pipelines

What does this MR do?

This MR introduces workflow:rules to be evaluated and dynamically determine whether a pipeline should be run or skipped. It adds another Pipeline::Chain to the pipeline execution sequence that optionally moves a Ci::Pipeline to skipped, effectively the same result as Chain::Skip.

Closes #29654 (closed)

This MR also includes the entirety of !18709 (closed), which can be merged before this.

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

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