POC for snowplow micro validation in feature specs

Goal

Attempt to get one feature spec example in ee/spec/features/registrations/saas to validate the entire funnel events seen in #422348 (closed) using snowplow micro as a collector and then validating against it.

At the end we should have a local development only way to run the example spec that will validate the events were fired for the entire funnel. This functionality will likely be controlled by an environment variable at first so that it will only run on demand and not in CI until we vett this concept fully.

the setup may look something like this:

  it 'registers the user and creates a group and project reaching onboarding', :sidekiq_inline, :clean_snowplow_queue do
      sign_up_method.call

      expect_to_see_welcome_form
      expect_to_send_iterable_request

      fills_in_welcome_form
      click_on 'Continue'

      expect_to_see_group_and_project_creation_form

      fills_in_group_and_project_creation_form
      click_on 'Create project'

      expect_to_be_in_continuous_onboarding

      click_on 'Ok, let\'s go'

      expect_to_be_in_learn_gitlab

      expect_to_have_all_defined_events # this would perform the snowplow verification
    end

See !105630 for ideas