Merge request activity filter

What does this MR do and why?

Added a merge request activity filter to the merge request overview tab. This will filter out certain activity types for the user.

Note: The listbox component will be updated to add things like scrim/hover state in upcoming milestones

Activity groups:

All MR activity types (I think)	How they're grouped/displayed in filter
approved	Approval
unapproved	Approval
commit	Commits & branches
branch	Commits & branches
cherry-pick	Commits & branches
merge (is this automatic merge when pipeline finishes?)	Merge request status
merged	Merge request status
opened	Merge request status
closed	Merge request status
assignee	Assignees & reviewers
reviewer	Assignees & reviewers
title	Edits
edit description	Edits
task	Edits
label	Labels
cross reference	Mentions
comment	Comments
outdated (is this when someone comment on an outdated diff?)	Comments
lock	Lock status
unlock	Lock status
due date	Tracking
start date	Tracking
time tracking	Tracking
milestone	Tracking

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Enable mr_activity_filters feature flag

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

#387070 (closed)