Smarter system notes for description edits

Editing a description will create a new system note now, which is great!

We should be smarter about when we generate these notes. For example, if the same user edits the description of an issue 1+ times within a 10 minute window, we do not need to show a new system note every time. Typically it is to correct a typo or add another line that you forgot. Adding a system note each time pollutes the description timeline.

Design

Let's join that notes if they fit some conditions like:

1. Notes go after each other (no any other notes/comments among them).

2. Notes have the same type.

3. Notes lay in a small time window (1 minute - 10 minutes).

it would be something like

@blackst0ne changed the description 7 times within 5 minutes, 12 days ago

• This will be for issues, merge requests, and epics.
• Update: This will work for merge requests when the Vue refactor is complete. See https://gitlab.com/gitlab-org/gitlab-ce/issues/47694#note_80801629