Leverage CSS vs. JS for pipeline padding

What does this MR do?

• Refactors away from a resize-JavaScript listener approach in favor of CSS-only so that the pipelines UI has the correct left-padding by default

Screenshots (strongly suggested)

Video of new behaviour:

Original_behaviour

Instance uses

Sidebar style accounted for

Container style accounted for

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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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

Related to #239446 (closed)