FY21-Q4 Dev KR: Improve the LCP performance of 53 routes in Dev that 80% (42) are below 2.5s => 20%

Dashboard - https://dashboards.gitlab.net/d/BxlP7whMk/sitespeed-lcp-dev-leaderboard?orgId=1 (Starting value 53%)

Selected Routes for Dev - https://docs.google.com/spreadsheets/d/19VENf6d54vuQn7RWjGbA4j2yCgjnNnHHzZ0FZqgonPU/edit#gid=1729646984