Upgrade to Node 14 LTS

What does this MR do?

Use a supported version of the base container. Node 14 is the current version with the longest support timeline. In order to adjust to the new environment, this meant changing the pip bootstrapping. To meet the size requirements, I removed build-base package set.

What are the relevant issue numbers?

gitlab-org/gitlab#250330 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• [NA] Documentation created/updated for GitLab EE, if necessary
• [NA] Documentation created/updated for this project, if necessary
• [NA] Documentation reviewed by technical writer or follow-up review issue created
• [NA] Tests added for this feature/bug
• [NA] Job definition updated, if necessary
  • [NA] Auto-DevOps template
  • [NA] Job definition example
  • [NA] CI Templates
• Conforms to the code review guidelines
• [NA] Conforms to the Go guidelines
• Security reports checked/validated by reviewer