Revert b6002a796

Revert b6002a796

This removes "Add Result Cache executor node".  It seems that something
weird is going on with the tracking of cache hits and misses as
highlighted by many buildfarm animals.  It's not yet clear what the
problem is as other parts of the plan indicate that the cache did work
correctly, it's just the hits and misses that were being reported as 0.

This is especially a bad time to have the buildfarm so broken, so
reverting before too many more animals go red.

Discussion: https://postgr.es/m/CAApHDvq_hydhfovm4=izgWs+C5HqEeRScjMbOgbpC-jRAeK3Yw@mail.gmail.com