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/params/smt_params_helper.pyg

@@ -86,6 +86,7 @@ def_module_params(module_name='smt',
 			  ('arith.nl.cross_nested', BOOL, True, 'enable cross-nested consistency checking'),
 			  ('arith.nl.log', BOOL, False, 'Log lemmas sent to nra solver'),
                           ('arith.propagate_eqs', BOOL, True, 'propagate (cheap) equalities'),
+			  ('arith.epsilon', DOUBLE, 1.0, 'initial value of epsilon used for model generation of infinitesimals'),
                           ('arith.propagation_mode', UINT, 1, '0 - no propagation, 1 - propagate existing literals, 2 - refine finite bounds'),
                           ('arith.branch_cut_ratio', UINT, 2, 'branch/cut ratio for linear integer arithmetic'),
                           ('arith.int_eq_branch', BOOL, False, 'branching using derived integer equations'),