perf dlfilter: Add a test for object_code()

Extend the "dlfilter C API" test to test
perf_dlfilter_fns.object_code().

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20230928091033.33998-1-adrian.hunter@intel.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>