Why this change?
When running system tests on our CI, we have been occasionally seeing
server errors like:
```
Error encountered while proccessing /stylesheets/desktop_e58cf7f686aab173f9b778797f241913c2833c39.css
NoMethodError: undefined method `+' for nil:NilClass
/__w/discourse/discourse/vendor/bundle/ruby/3.2.0/gems/actionpack-7.0.7/lib/action_dispatch/journey/path/pattern.rb:139:in `[]'
/__w/discourse/discourse/vendor/bundle/ruby/3.2.0/gems/actionpack-7.0.7/lib/action_dispatch/journey/router.rb:127:in `block (2 levels) in find_routes'
/__w/discourse/discourse/vendor/bundle/ruby/3.2.0/gems/actionpack-7.0.7/lib/action_dispatch/journey/router.rb:126:in `each'
/__w/discourse/discourse/vendor/bundle/ruby/3.2.0/gems/actionpack-7.0.7/lib/action_dispatch/journey/router.rb:126:in `each_with_index'
/__w/discourse/discourse/vendor/bundle/ruby/3.2.0/gems/actionpack-7.0.7/lib/action_dispatch/journey/router.rb:126:in `block in find_routes'
/__w/discourse/discourse/vendor/bundle/ruby/3.2.0/gems/actionpack-7.0.7/lib/action_dispatch/journey/router.rb:123:in `map!'
/__w/discourse/discourse/vendor/bundle/ruby/3.2.0/gems/actionpack-7.0.7/lib/action_dispatch/journey/router.rb:123:in `find_routes'
/__w/discourse/discourse/vendor/bundle/ruby/3.2.0/gems/actionpack-7.0.7/lib/action_dispatch/journey/router.rb:32:in `serve'
/__w/discourse/discourse/vendor/bundle/ruby/3.2.0/gems/actionpack-7.0.7/lib/action_dispatch/routing/route_set.rb:852:in `call'
```
While looking through various Rails issues related to the error above, I
came across https://github.com/rails/rails/pull/27647 which is a fix to
fully initialize routes before the first request is handled. However,
the routes are only fully initialize only if `config.eager_load` is set
to `true`. There is no reason why `config.eager_load` shouldn't be `true` in the
CI environment and this is what a new Rails 7.1 app is generated with.
What does this change do?
Enable `config.eager_load` when `env["CI"]` is present
bf3e121323