Replace custom replace utility with the stdlib's replace algorithm.

This removes the custom `replaceAll` function, replacing it with
`std::replace` from the stdlib's `<algorithm>` header.

This also removes the respective unit test.

More importantly, this removes the dependency on the
`<boost/algorithm/string.hpp>` header in the `string_util.hpp` header.

unit_tests/algorithms/string_util.cpp

@@ -34,16 +34,6 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 BOOST_AUTO_TEST_SUITE(string_util)
 
-BOOST_AUTO_TEST_CASE(replace_all_test)
-{
-    std::string input{"ababababababa"};
-    const std::string sub{"a"};
-    const std::string other{"c"};
-    replaceAll(input, sub, other);
-
-    BOOST_CHECK_EQUAL(input, "cbcbcbcbcbcbc");
-}
-
 BOOST_AUTO_TEST_CASE(json_escaping)
 {
     std::string input{"\b\\"};