[RF] Add test for RooAbsCollection's hash-assisted find.
[RF] Add test for RooAbsCollection's hash-assisted find.

olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root