[Meta] Make GitLab FE Faster (Network Issues Affecting FE)

This is all using Issue gitlab-ce#1 as an example. This is also using disabled cache because disabled cache signifies a users first experience, and will be us at our slowest in theory.

• High Latency: https://gitlab.com/gitlab-org/gitlab-ce/issues/38127
• Slow Network: https://gitlab.com/gitlab-org/gitlab-ce/issues/38128
• DeCruft Main.js: https://gitlab.com/gitlab-org/gitlab-ce/issues/38130
• Remove the Vue Runtime Template Compiler: https://gitlab.com/gitlab-org/gitlab-ce/issues/34371
• Make JS Higher Priority Somehow: https://gitlab.com/gitlab-org/gitlab-ce/issues/38159
• Make Some Scripts UnDeffered (but not async): https://gitlab.com/gitlab-org/gitlab-ce/issues/38160
• Make GitLab Requests faster: https://gitlab.com/gitlab-org/gitlab-ce/issues/38161
• Only load the needed locale file and not all translations in all languages https://gitlab.com/gitlab-org/gitlab-ce/issues/38470

Notice that you have a light blue and and a dark blue. The light blue is the request and the dark blue is the content downloading. Which is a long time for Rails to compute stuff. This is backend optimizations.

cc @stanhu @ernstvn