Enables Bootsnap to GitLab (development)

What does this MR do?

1. Adds bootsnap to the development and test dependency
2. Loads it with a rescue block, so it becomes optional but doesn't depend on specific RAILS_ENV. That in practice means if bootsnap is available in the gem folder, it will use it. This was done in that way so we can optionally test/use it even in a test machine with an omnibus install.

Are there points in the code the reviewer needs to double check?

Do we need developer specific documentation or mention anywhere we are using bootsnap?

What are the relevant issue numbers?

Closes #45230 (closed)