convert reduce-args to a simplifier

- convert reduce-args to a simplifier. Currently exposed as reduce-args2 tactic until the old tactic code gets removed.
- bug fixes in model_reconstruction trail
  - allow multiple defs to be added with same pool of removed formulas
  - fix tracking of function symbols instead of expressions to filter replay
- add nla_divisions to track (cheap) divisibility lemmas.
-

src/math/lp/CMakeLists.txt

@@ -34,6 +34,7 @@ z3_add_component(lp
     nla_basics_lemmas.cpp
     nla_common.cpp
     nla_core.cpp
+    nla_divisions.cpp
     nla_grobner.cpp
     nla_intervals.cpp
     nla_monotone_lemmas.cpp