add option to control epsilon #7791

#7791 reports on using model values during lex optimization that break soft constraints.
This is an artifact of using optimization where optimal values can be arbitrarily close to a rational.
In a way it is by design, but we give the user now an option to control the starting point for epsilon when converting infinitesimals into rationals.

src/math/lp/lp_settings.h

@@ -242,6 +242,7 @@ private:
 public:
     unsigned         limit_on_rows_for_hnf_cutter = 75;
     unsigned         limit_on_columns_for_hnf_cutter = 150;
+    mpq              m_epsilon = mpq(1);
 private:
     unsigned         m_nlsat_delay = 0;
     bool             m_enable_hnf = true;