Incident Tag MVC Frontend

Implement the designs included in the Proposal in the Epic.

Suggested implementation breakdown

1. Display Incident Tag badge in timeline. (initially does nothing without dummy data, since the field is optional).
2. Add Incident Tag to the 'add item' and 'edit item' forms. (after !102999 (merged) is merged).
3. Add Incident Tag help popup to timeline add/edit forms.
4. Allow multiple badges to be displayed on the timeline events list (#360315 (comment 1232570746)

Availability and Testing

1. Unit tests - required:
   • Ensure every new component behaves as expected
   • All new components are displayed
   • Dropdown shows default option, is clickable and render option list when clicked on
   • help popover shows correct text when clicked on (or hover over?)
   • In the new timeline event, badge component is displayed, and has appropriate tag name
   • When comment textarea is empty, save button is disabled
2. Feature tests - required:
   • When click on event tag dropdown and select an option, default event text is displayed in comment textarea
   • Saving the event creates a new timeline event item that has correct badge, correct comment text and timeline
   • User can also create a new timeline event item with custom comment, when saved new timeline event item has the correct comment
   • User can edit the new timeline event item
   • User can delete the new timeline event item
   • User can add event with multiple tags
   • User can add event with 0 tag
3. E2E test - not required, triggering e2e:package-and-test in new MR at least once is recommended