feat(css): Add absolute position utility classes

What does this MR do?

Adds a the following utility class for absolute positioning:

• gl-top-6
• gl-top-7
• gl-right-2
• gl-right-3
• gl-right-6
• gl-bottom-2
• gl-bottom-3
• gl-bottom-5
• gl-bottom-7
• gl-left-2
• gl-left-3
• gl-left-7

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines.
• GitLab UI's contributing guidlines.
• If it changes a Pajamas-compliant component's look & feel, the MR has been reviewed by a UX designer.
• If it changes GitLab UI's documentation guidelines, the MR has been reviewed by a Technical Writer.
• If the MR changes a component's API, integration MR(s) have been opened in the following projects to ensure that the @gitlab/ui package can be upgraded quickly after the changes are released:
  • GitLab: mr_url
  • Customers Portal: mr_url
  • Status Page: mr_url
• Added the ~"component:*" label(s) if applicable.