FY21-Q4 KR: Reduce MR pipeline duration from 64 to 45 minutes => 52%

As measured by

Average merge request pipeline duration for GitLab monorepo

Plan

• Investigate bottleneck jobs for optimization opportunities
• Bottleneck jobs:
  1. Consider making the CI_PRE_CLONE_SCRIPT step faster: gitlab-org/gitlab#276220 (closed)
  2. setup-test-env job duration increased from 7.4 minutes on 2020-08-20 to 10.3 minutes on 2020-11-03: gitlab-org/gitlab#276217 (closed)
  3. compile-production-assets job duration increased from 19 minutes on 2020-09-04 to 21 minutes on 2020-11-03: gitlab-org/gitlab#276218 (closed)
  4. Improving generation of frontend-fixtures: gitlab-org/gitlab#217916 (closed)
  5. Migration spec job duration is increasing: gitlab-org/gitlab#237841 (closed)
  6. review-build-cng job duration increased from 27.3 minutes on 2020-08-24 to 29.4 minutes on 2020-10-28: gitlab-org/gitlab#276225 (closed)
  7. review-qa-smoke job duration increased from 8 minutes on 2020-08-04 to 10 minutes on 2020-10-29: gitlab-org/gitlab#276226 (closed)
  8. jest
  9. qa frontend node:10
• Rubocop not using cache: gitlab-org/gitlab#254233 (closed)
• Improve the duration of GitLab E2E pipelines that run package-and-qa to increase efficiency for SETs: gitlab-org&5230