Investigate why ls with wandbfsspec takes longer than with fsspec

[alvarobartt]

When we run pytest tests/ --durations 0 -s we see the following output:

===================================================================== test session starts =====================================================================
platform linux -- Python 3.9.13, pytest-7.1.2, pluggy-1.0.0
rootdir: /workspaces/wandbfsspec
collected 5 items                                                                                                                                             

tests/test_core.py .....

====================================================================== slowest durations ======================================================================
0.65s call     tests/test_core.py::TestWandbFileSystem::test_ls
0.56s call     tests/test_core.py::TestWandbFileSystem::test_modified
0.16s call     tests/test_core.py::TestWandbFileSystem::test_open
0.15s call     tests/test_core.py::TestWandbFileSystem::test_ls_from_fsspec
0.15s call     tests/test_core.py::TestWandbFileSystem::test_open_from_fsspec

(10 durations < 0.005s hidden.  Use -vv to show these durations.)
====================================================================== 5 passed in 2.14s ======================================================================

where the elapsed time to run ls over the same directory with fsspec is much faster than the one with wandbfsspec.