Create module for Internal Events

What does this MR do and why?

We would like the source location of where an event was triggered to be sent in the category property in Snowplow events.

In order to make it simple to get this information we provide this module that automatically gets the self.class.name and use it as category.

The MR also change a single use of Gitlab::InternalEvents.track_event to use the new module.

With the new module you can now call Internal Events like this:

module TestModule
  class ClassThatTracks
    include Gitlab::InternalEventsTracking

    def do_it
      # Do important work here

      track_internal_event('my_event', project: Project.first, user: User.last)
    end
  end
end

Instead of like this:

module TestModule
  class ClassThatTracks
    def do_it
      # Do important work here

      Gitlab::InternalEvents.track_event('my_event', project: Project.first, user: User.last)
    end
  end
end

Documentation will be included in a follow up MR.

So will a change to danger to make sure analytics instrumentation gets tagged for review.

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Related to #435200 (closed)