POSIX: Implement performant filesystem layer/view of DSS S3 object storage

[hroogi]

Currently DSS Support S3 based APIs to acccess the cluster.
rclone and s3fs are some of the implementations, but they severely degrade the DSS performance.

We need to add filesystem/posix layer for this S3 storage APIs, which is also performant
This is highly useful for traditional applications using filesystems for their storage requirements.