feat(library/tactic): add disj_hyp_tactic

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/tactic): add absurd_tactic

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library/tactic): remove duplicate code, add add_proofs

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(util/list): bug in map template

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/tactic): add unfold tactic

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/hidden_defs): hidden definitions are just hints for tactics and solvers

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/tactic): add unfold_tactic() that unfolds every non-hidden definition

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(library/rewriter): add lambda_rewrite tests