WIP: Extract config processor from `Ci::Pipeline`

What does this MR do?

In this MR we are moving the usage of config_processor outside Ci::Pipeline into a pipeline chain step InitializeConfigProcessor. From that point on the config_processor will be available in the @command context throughout the pipeline creation algorithm.

This MR targets currently the extract-ci-config-from-pipeline as it was branched from that initial refactoring.

Related issue: #35727 (closed)

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