Track smart_holder PR #5286: Fix HAVE vs HAS naming mishap (PYBIND11_HAS_INTERNALS_WITH_SMART_HOLDER_SUPPORT)

pybind/pybind11#5286

Systematic, trivial name change:

```diff
-PYBIND11_HAVE_INTERNALS_WITH_SMART_HOLDER_SUPPORT
+PYBIND11_HAS_INTERNALS_WITH_SMART_HOLDER_SUPPORT
```

This is for internal consistency. There are no `PYBIND11_HAVE` macros, but 10 unique `PYBIND11_HAS` macros:

```
$ git grep 'define PYBIND11_HAS' | sed 's/.*define PYBIND11_HAS/PYBIND11_HAS/' | cut -d' ' -f1 | sort | uniq
```
```
PYBIND11_HAS_EXPERIMENTAL_FILESYSTEM
PYBIND11_HAS_EXP_OPTIONAL
PYBIND11_HAS_FILESYSTEM
PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
PYBIND11_HAS_INTERNALS_WITH_SMART_HOLDER_SUPPORT
PYBIND11_HAS_OPTIONAL
PYBIND11_HAS_STD_LAUNDER
PYBIND11_HAS_STRING_VIEW
PYBIND11_HAS_U8STRING
PYBIND11_HAS_VARIANT
```

PiperOrigin-RevId: 659556864

Author: rwgk

pybind11_protobuf/native_proto_caster.h

@@ -91,7 +91,7 @@ struct type_caster<
     : public pybind11_protobuf::proto_caster<
           ProtoType, pybind11_protobuf::native_cast_impl> {};
 
-#if defined(PYBIND11_HAVE_INTERNALS_WITH_SMART_HOLDER_SUPPORT)
+#if defined(PYBIND11_HAS_INTERNALS_WITH_SMART_HOLDER_SUPPORT)
 
 template <typename ProtoType>
 struct copyable_holder_caster_shared_ptr_with_smart_holder_support_enabled<
@@ -103,7 +103,7 @@ struct move_only_holder_caster_unique_ptr_with_smart_holder_support_enabled<
     ProtoType, enable_if_t<std::is_base_of<::google::protobuf::Message, ProtoType>::value>>
     : std::false_type {};
 
-#endif  // PYBIND11_HAVE_INTERNALS_WITH_SMART_HOLDER_SUPPORT
+#endif  // PYBIND11_HAS_INTERNALS_WITH_SMART_HOLDER_SUPPORT
 
 // NOTE: If smart_holders becomes the default we will need to change this to
 //    type_caster<std::unique_ptr<ProtoType, D>, ...