Investigate accidental useData loop still using CPU after closing tab

[tjcouch-sil]

We had a useData that was constantly causing rerenders because the selector was not wrapped in a useMemo.

Tim closed all his dock views and was still having immensely high CPU usage on the renderer. We would expect closing the hello world tab to drop the CPU usage. I wonder if some useData subscriptions are not properly getting cleaned up in the useEffect returns or if rc-dock's tabs don't actually delete the react components underneath. Or maybe it was some strange loop of dependencies that just kept the callbacks running. Please investigate

[tjcouch-sil]

This may be fixed by #578!