Implement allowing empty needs for jobs in DAG pipelines

What does this MR do?

This is the second MR of implementing empty needs for jobs in DAG pipelines

discussion: !21306 (comment 261625664)

This MR targets the branch of !22245 (merged) to provide clean diff.

TODO: Change the target to master after merging !22245 (merged) .

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This MR will allow jobs to have needs: [] configuration.

Those jobs will start immediately without waiting previous stages.

ref: #30631 (closed)

previous discussions: !21306 (closed)

Screenshots

There are screenshots in old MR: !21306 (closed)

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