[All] make Solver.Delayed used in all the apis

src/arith.ml

src/arith.mli

src/bool.ml

src/bool.mli

src/equality.ml

src/equality.mli

src/inputlang/altergo/popop_of_altergo.ml

src/inputlang/dimacs_cnf/dimacs.mll

src/scheduler.ml

src/scheduler_queue.ml

src/scheduler_queue.mli

src/solver.ml

src/solver.mli

src/uninterp.ml

src/uninterp.mli

src/variable.mli

tests/tests_bool.ml