gh-111178: fix UBSan failures in `Modules/_ctypes` (#129071)

gh-111178: fix UBSan failures in `Modules/_ctypes` (#129071)

This fixes UBSan failures for the following objects:

- `DictRemoverObject` and `StructParamObject`,
- `CDataObject` and `CFieldObject`, and
- `PyCFuncPtrObject` and `PyCArgObject`.

On the default build, we convert the `LOCK_PTR` and `UNLOCK_PTR` macros to
functions with an unused parameter to ease "unused variable" compiler warnings
suppression. Finally, we also remove some redundant casts to `PyObject *`.