UI hangs / is non responsive when running a query/profiling a big model

[bcolloran]

To Reproduce

• start a query on a large enough dataset that it takes a while for profiling results to return e.g. select * from nyc311_reduced
• try hovering on things that should have tooltips, clicking on "sort" dropdowns, expanding/collapsing sidebar items
• nothing happen, UI is frozen; no tooltips or other interactions
• also, the spinner does not start right away, it hangs for a while before starting up (when profile results seem to start streaming in)

Expected behavior

• starting the query immediately starts the activity spinner
• the UI remains responsive for things like tooltips, deleting existing models (other menu actions), expand/collapse, etc