Remove Tee code, move to _deadcode.

src/backend/commands/explain.c

src/backend/executor/Makefile

src/backend/executor/_deadcode/nodeTee.c

src/backend/executor/execAmi.c

src/backend/executor/execMain.c

src/backend/executor/execProcnode.c

src/backend/executor/execTuples.c

src/backend/nodes/outfuncs.c

src/backend/nodes/print.c

src/include/executor/nodeTee.h

src/include/nodes/execnodes.h

src/include/nodes/nodes.h

src/include/nodes/plannodes.h