implement our own url_to_fs for fsspec storage

[d-v-b]

we are currently using fsspec.url_to_fs to convert string URLs to fsspec filesystems. url_to_fs can be very slow (~25s in some cases), which adds unnecessary latency given the simplicity of the URLs we need to handle. So we should implement our own version of this function that runs in much less time.

I opened an issue about this upstream: fsspec/filesystem_spec#1768

[d-v-b]

looks like the actual problem is the time required for gcsfs to resolve credentials, not url_to_fs itself. I will close this