Add Code Insights built-in dashboards

Created by: vovakulikov

Closes https://github.com/sourcegraph/sourcegraph/issues/22218

Backgound

This PR extends useDashobards() hook (get operation for the dashboards) by "built-in" insights dashboards. These dashboards are not stored in user or organization settings. They are derived and can't be deleted or moved in another organization's scope.

There are three types of built-in dashboards

1. All insights Combined insights from all dashboards (personal and custom) and organizations.

2. Personal Insights from user personal settings

3. Organization level Insights from particular org settings. For example in case when you have two organizations orgA and orgB you have two dashboards with the same names.

You can find information on how these types would work by this Figma design layout

https://www.figma.com/file/g5lSlPBnHt00wCogjRFnt5/RFC-398%3A-Easily-Viewing-and-Sharing-Code-Insights-WIP?node-id=275%3A1628

UI for this functionality will be started in the next Code insights Dasbhoards story tickets Next ticket - https://github.com/sourcegraph/sourcegraph/issues/22225 Tracking issue - https://github.com/sourcegraph/sourcegraph/issues/22215