Convert epics_usage_total_unique_counts_monthly to Internal events

Problem

In Recreate Redis Counters using Snowplow events -... (#366827 - closed) and Recreate Redis Counters using Snowplow events -... (#370373 - closed) we converted all events for the epics_usage_total_unique_counts_monthly to mirror to Snowplow, but now since we're using Internal Events we ideally want to convert to this.

Desired Outcome

All backend events listed in epics_usage_total_unique_counts_monthly are converted to internal events.

The one frontend event in this is separated into #421594 (closed)

Potential Solution

TBD

Already migrated events:

• g_project_management_epic_created
• project_management_users_unchecking_epic_task
• project_management_users_checking_epic_task
• g_project_management_users_updating_epic_titles
• g_project_management_users_updating_epic_descriptions
• g_project_management_users_creating_epic_notes
• g_project_management_users_updating_epic_notes
• g_project_management_users_destroying_epic_notes
• g_project_management_users_awarding_epic_emoji
• g_project_management_users_removing_epic_emoji
• g_project_management_users_setting_epic_start_date_as_fixed
• g_project_management_users_updating_fixed_epic_start_date
• g_project_management_users_setting_epic_start_date_as_inherited
• g_project_management_users_setting_epic_due_date_as_fixed
• g_project_management_users_updating_fixed_epic_due_date
• g_project_management_users_setting_epic_due_date_as_inherited
• g_project_management_epic_issue_added
• g_project_management_epic_issue_removed
• g_project_management_epic_issue_moved_from_project
• g_project_management_users_updating_epic_parent
• g_project_management_epic_closed
• g_project_management_epic_reopened
• 'g_project_management_issue_promoted_to_epic'
• g_project_management_users_setting_epic_confidential
• g_project_management_users_setting_epic_visible
• g_project_management_epic_users_changing_labels
• g_project_management_epic_destroyed
• g_project_management_epic_cross_referenced
• g_project_management_epic_related_added
• g_project_management_epic_related_removed
• g_project_management_epic_blocking_added
• g_project_management_epic_blocking_removed
• g_project_management_epic_blocked_added
• g_project_management_epic_blocked_removed

FE event:

• g_project_management_users_epic_issue_added_from_epic