Migrate users_updating_work_item_title to Internal Events

What does this MR do and why?

Migrate users_updating_work_item_title to Internal Events

This migrates the existing work item title tracking event to Internal Events framework and adds work item type as a label, following the pattern from the reference MR for users_creating_work_items.

Related to #553535

🎯 Key Features

• Work Item Type Labeling: Events are labeled with the work item base type (epic, issue, task, etc.)
• Epic-Specific Filtering: New metric specifically tracks epic title updates using label filtering
• Backward Compatibility: HLL Redis key overrides ensure compatibility with existing systems
• Future-Proof: Uses Internal Events framework following GitLab's current best practices

🧪 Testing Instructions

To test the implementation:

1. Run the Internal Events monitor:

   bundle exec rails r scripts/internal_events/monitor.rb users_updating_work_item_title

2. Update the title of an epic work item

3. Verify the event is tracked with label: epic

📊 Metrics Created

• redis_hll_counters.count_distinct_user_id_from_updating_work_item_title_epic - Epic-specific title updates
• counts_weekly.aggregated_metrics.users_updating_work_item_title - Weekly work item title updates
• counts_monthly.aggregated_metrics.users_updating_work_item_title - Monthly work item title updates

MR acceptance checklist

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Related to #553535