s3fs support for S3V4 signer

Hey, I'm curious if you would accept a contribution to support the pluggable (rest) S3V4 signer? That's pretty much delegating https://github.com/duckdb/duckdb-httpfs/blob/main/extension/httpfs/s3fs.cpp#L26 to a service.

Here is an example from Iceberg https://iceberg.apache.org/javadoc/1.6.0/org/apache/iceberg/aws/s3/signer/S3V4RestSignerClient.html or https://github.com/apache/iceberg-python/blob/1c0e2b04c383e5d90118ffce2066dcdb95193c4a/pyiceberg/io/fsspec.py#L89-L117 (might be easier to read).