[SMTChecker] Split SMTChecker into SMTEncoder and BMC

test/libsolidity/smtCheckerTests/complex/slither/const_state_variables.sol

@@ -58,3 +58,4 @@ contract MyConc{
 // Warning: (834-839): Assertion checker does not yet support the type of this literal (literal_string "abc").
 // Warning: (874-879): Underflow (resulting value less than 0) happens here.
 // Warning: (874-879): Overflow (resulting value larger than 2**256 - 1) happens here.
+// Warning: (985-1002): Overflow (resulting value larger than 2**256 - 1) happens here.

test/libsolidity/smtCheckerTests/modifiers/modifier_code_after_placeholder.sol

@@ -8,8 +8,6 @@ contract C
 		require(x > 0);
 		_;
 		// Fails because of overflow behavior.
-		// Overflow is not reported because this assertion prevents
-		// it from reaching the end of the function.
 		assert(x > 1);
 	}
 
@@ -19,4 +17,4 @@ contract C
 	}
 }
 // ----
-// Warning: (245-258): Assertion violation happens here
+// Warning: (136-149): Assertion violation happens here