…81de4e0ae41d861a5c46903968f7b27

The pybind11k `return_value_policy_pack` and `function_record` changes were backed out.

The net diffs to PR pybind#4597 are merely:

```diff
+#define PYBIND11_HAS_TYPE_CASTER_STD_FUNCTION_SPECIALIZATIONS
```

```diff
-    explicit func_wrapper_base(func_handle &&hf) noexcept : hfunc(hf) {}
+    explicit func_wrapper_base(func_handle &&hf) noexcept : hfunc(std::move(hf)) {}
```

```
/__w/pybind11/pybind11/include/pybind11/functional.h:47:67: error: passing result of std::move() as a const reference argument; no move will actually happen [performance-move-const-arg,-warnings-as-errors]
   47 |     explicit func_wrapper_base(func_handle &&hf) noexcept : hfunc(std::move(hf)) {}
      |                                                                   ^~~~~~~~~~  ~
/__w/pybind11/pybind11/include/pybind11/functional.h:23:8: note: 'func_handle' is not move assignable/constructible
```

…ions_sh