Moves every fixture source file from
spec/javascripts to spec/frontend

Related issue:
https://gitlab.com/gitlab-org/gitlab-ee/issues/6565

The `#reload` makes to load all objects into memory,
and the main purpose of `#reload` is to drop the association cache.

The `#reset` seems to solve exactly that case.

We also enable the rubocop that makes it mandatory

This style change enforces `return if ...` instead of
`return nil if ...` to save maintainers a few minor review points

This change allows the GitLab rails and sidekiq components to receive
tracing spans from upstream services such as Workhorse and pass these
spans on to downstream services including Gitaly and Sidekiq.

This change will also emit traces for incoming and outgoing requests
using the propagated trace information. This will allow operators and
engineers to view traces across the Workhorse, GitLab Rails, Sidekiq and
Gitaly components.

Additional intra-service instrumentation will be added in future
changes.

Updates specs to use new rails5 format.

The old format:
`get :show, { some: params }, { some: headers }`

The new format:
`get :show, params: { some: params }, headers: { some: headers }`

This Cop enforces the rule that injecting EE modules (using prepend,
include, or extend) is done by placing the injection on the last line of
a file, instead of somewhere in the middle. By placing these lines at
the very end, merge conflicts will not happen.