Export internal events tests into common code

config/events/g_project_management_issue_created.yml

...tlab/usage_data_counters/issue_activity_unique_counter.rb

...usage_data_counters/issue_activity_unique_counter_spec.rb

...ta_counters/merge_request_activity_unique_counter_spec.rb

spec/models/issue_spec.rb

spec/models/work_item_spec.rb

..._examples/controllers/internal_event_tracking_examples.rb

..._examples/controllers/snowplow_event_tracking_examples.rb

.../usage_data_counters/issuable_activity_shared_examples.rb