Add option to choose solver

test/cmdlineTests/model_checker_solvers_wrong2/args

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+--model-checker-engine all --model-checker-solvers z3, smtlib2

test/cmdlineTests/model_checker_solvers_wrong2/err

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+"smtlib2" is not found.

test/cmdlineTests/model_checker_solvers_wrong2/exit

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+1

test/cmdlineTests/model_checker_solvers_wrong2/input.sol

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+// SPDX-License-Identifier: GPL-3.0
+pragma solidity >=0.0;
+contract test {
+	function f(uint x) public pure {
+		assert(x > 0);
+	}
+}