Add the ability to annotate some certain areas of the profile

When working and collaborating, it's very useful to annotate some certain areas and make sure that we preserve it when saved/shared. That way either we can make the collaboration easier or we can add ourselves some notes/bookmarks to make sure that we don't forget.

It looks like Chrome performance panel also recently added this feature: https://developer.chrome.com/blog/devtools-annotations
Things we can do:
- Annotate a time range
- Annotate an entry
- Add connections between entries
- Delete and hide annotations
- Save the profile with/without the annotations

It would be great to have something similar to this so we can mark some specific areas.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-822)