[SMTChecker] Report values for block, msg and tx variables in counterexamples

test/cmdlineTests/model_checker_targets_assert_chc/err

@@ -1,13 +1,13 @@
 Warning: CHC: Assertion violation happens here.
 Counterexample:
 arr = []
-a = 0
+a = 0x0
 x = 0
 
 Transaction trace:
 test.constructor()
 State: arr = []
-test.f(0, 1)
+test.f(0x0, 1)
   --> model_checker_targets_assert_chc/input.sol:11:3:
    |
 11 | 		assert(x > 0);