clang-tidy readability-qualified-auto (#3702)

* Adding readability-qualified-auto to .clang-tidy

Ported from @henryiii's https://github.com/pybind/pybind11/pull/3683/commits/287527f705c8badee8ba9f6278d691fe0450ae43

* fix: support Python < 3.6

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>

tests/test_pytypes.cpp

@@ -146,7 +146,7 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("return_capsule_with_name_and_destructor", []() {
         auto capsule = py::capsule((void *) 12345, "pointer type description", [](PyObject *ptr) {
             if (ptr) {
-                auto name = PyCapsule_GetName(ptr);
+                const auto *name = PyCapsule_GetName(ptr);
                 py::print("destructing capsule ({}, '{}')"_s.format(
                     (size_t) PyCapsule_GetPointer(ptr, name), name
                 ));