Make insights dashboard page titles show the page title

Created by: Joelkw

Seems like a very small easy feature and useful for having open in multiple tabs – make the page title something like Dashboard title.... - Sourcegraph Code Insights perhaps? Could shorten the Sourcegraph Code Insights part to Code Insights maybe. What's important is the title comes before the thing that'll be non-unique (the "- Sourcegraph Code..." suffix).

Right now it's just "insights" regardless of dashboard page:

(We should also perhaps have edit and creation titles that use the title of the insight?)