Streaming: jittery results display on long-running searches

Created by: lguychard

On a long-running streaming search like RouteHandler timeout:20s count:1000, notice that the results are pushed down three times:

1. When the filters row is rendered
2. When the "skipped" toolbar item is rendered
3. When the repositories row is rendered

Item 2. would not happen on wider viewports, but I find the unstable UI with the actual results being pushed further and further below the fold frustrating (especially if I start reading the code of a result while the search is still running, and it suddenly skips down). Maybe something we only want to tackle with the results page refactor, though?

cc @rrhyne @limitedmage

https://user-images.githubusercontent.com/1741180/105499822-4ff81000-5cc2-11eb-9a0a-5cfecb5fbbb6.mp4