Performance: Add/Enable Bootsnap for all Rails based container

This pulls in a matching change from the task-runner chart to Unicorn & Sidekiq.

We explicitly add this to the dependencies container as well, as it has a large impact there, and it will "ideally" only ever have to start rails/rake once.

Best performance is pending the following stack of changes:

• upstream release of shopify/bootsnap
• update in gitlab-org/gitlab
• gitlab-org/build/CNG!376 (merged)

Closes #1779 (closed)

~~Currently Blocked and should not be merged, less we negatively impact performance of single-run containers such as Unicorn.~~

Performance tests appear to indicated a net-positive result on performance, even when the cache is not present.

cc @stanhu