ENH: add warning stacklevel when surfacing warnings from gdal.

In `_err.pyx` ``` cython if err_class == CE_Warning: with gil: warnings.warn(clean_error_message(err_msg), RuntimeWarning) return ``` warnings surfaced by GDAL are bubbled up through the python warning system. Ideally this should probably get a stacklevel argument back to the read file call rather than showing a trace to pyogrio internals. I'm not sure why there isn't a stacklevel currently, perhaps this is a case where it's not easy to deduce what hte stack level should be as it depends on how it is reached.