Track editable metrics for a merge request

Task:

Track the following metrics with HLL tracking

Action	Description
title	Changed the title of the MR
description	Changed the description of the MR
task	Checked / unchecked a task list item in the description
draft_added	Marked MR as a draft
draft_removed	Removed draft status from an MR
approval_rule_added	Added an approval rule specific to the MR
approval_rule_edited	Edited a project approval rule in the MR
approval_rule_removed	Deleted an approval rule from the MR