Function ignoreOldStyleInitWarnings

tests/pybind11_tests.h:88–98

template <typename F>
void ignoreOldStyleInitWarnings(F &&body) {
    py::exec(R"(
    message = "pybind11-bound class '.+' is using an old-style placement-new '(?:__init__|__setstate__)' which has been deprecated"

    import warnings
    with warnings.catch_warnings():
        warnings.filterwarnings("ignore", message=message, category=FutureWarning)
        body()
    )",
             py::dict(py::arg("body") = py::cpp_function(body)));
}

// See PR #5419 for background.
class TestContext {