Add workaround/fix for GGC 12 bound checking error

Issue: #5224

The `internals.registered_types_py...` line in pybind11.h triggers a
false-positive bounds checking warning in GCC 12.

This is discussed in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115824.

The workaround implemented is taken from suggestions in this discussion.

include/pybind11/pybind11.h

@@ -1380,7 +1380,19 @@ class generic_type : public object {
             } else {
                 internals.registered_types_cpp[tindex] = tinfo;
             }
+            // The following `GCC diagnostic` pragmas are used to suppress
+// warnings  about out-of-bounds array access in the following
+// code. The warnings are false positives. This bug affects GCC 12.
+//
+// This is discussed here:
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115824.
+//
+// The following fix is based on the the suggested workaround:
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Warray-bounds"
+#pragma GCC diagnostic ignored "-Wstringop-overread"
             internals.registered_types_py[(PyTypeObject *) m_ptr] = {tinfo};
+#pragma GCC diagnostic pop
         });
 
         if (rec.bases.size() > 1 || rec.multiple_inheritance) {