WIP: Implement allowing empty needs for jobs in DAG pipelines

NOTE!

This is just a basic proposal with so many missing tests and code smells, Work In Progress.

What does this MR do?

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

Those jobs will start immediately without waiting previous stages.

ref: #30631 (closed)

Questions:

• How should depend-lines between jobs in the pipeline graph look like? frontend

Screenshots

stages:
  - lint
  - test
  - deploy

lint1:
  stage: lint
  script:
    - sleep 5
    - echo lint1

test1:
  stage: test
  script:
    - sleep 10
    - echo test1

test2:
  stage: test
  needs: []
  script:
    - sleep 10
    - echo test2

deploy1:
  stage: deploy
  script:
    - sleep 10
    - echo deploy1

deploy2:
  stage: deploy
  needs: []
  script:
    - sleep 10
    - echo deploy2

deploy3:
  stage: deploy
  needs: ["lint1"]
  script:
    - sleep 10
    - echo deploy3

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