Adjust a couple of tests for new behavior (thus all of this might be backwards incomp...

Adjust a couple of tests for new behavior (thus all of this might be backwards incompatible to the point of being useless):
The counts in t/90join_torture.t are now 5*3, not 5*3*3, as a second join is not induced by search_related
The raw sql scan in t/prefetch/standard.t is just silly, won't even try to understand it
Just to maintain the TreeLike folding, I add a 3rd children join which was inserted by search_related before the code changes