Change CTA for adding insights to dashboard

[corywatilo]

After creating a new dashboard, the primary CTA is to add an insight. (This is the same for existing dashboards.)

As a user, I'm expecting to add an existing saved insight, not to be taken to create a new insight from scratch.

I'd prefer to see a list of saved insights that I can directly add to the new dashboard. (Sort of like this modal below, but displaying saved insights to be added directly to the dashboard I'm currently viewing.)

[clarkus]

As a user, I'm expecting to add an existing saved insight, not to be taken to create a new insight from scratch.

I think we should prompt for adding an existing or creating new. It's hard to know user intent, so providing a choice might be the most robust approach here. I think this came up during the recent dashboard work, but we didn't resolve it.

[clarkus]

I have a solution for this at https://www.figma.com/file/A9XRxeDm3ceikbenfTBGZl/Insights%2C-Dashboards%2C-%26-Project-Home?node-id=5%3A111082. It matches the workflow we use for creating a new insight from the insights feature, with the addition of "existing insight" option that lets you browse for an existing insight.