Code Insights: Introduce starred/favorite/pinned insights

Created by: vovakulikov

Background

At the moment our "All insights" dashboard is full of insights from all users in the account. Other dashboards also could have a big number of insights. I think it might be useful to be able to pin insights and show them on the separate dashboard-like "You favorite insights" or render them always on top of each dashboard that have at least one pinned/starred insight.

Input from @AlicjaSuska

I think that starring insights make sense:

• in general: I might be interested in a couple of insights from multiple dashboards and want to preview them more often. Creating a dashboard feels like an 'official' big deal and it's a longer flow. Starring would be quick and less of a headache for users.
• display starred at the top of every dashboard - good idea to provide some level of per-user customization to displaying dashboards
• better visibility on the 'All insights' dashboard. Although, I agree that we should add some grouping/filtering/searching to the 'all insights' page as well.