main/streams/streams: use copy_file_range() on Linux (#8413)

copy_file_range() is a Linux-specific system call which allows
efficient copying between two file descriptors, eliminating th

main/streams/streams: use copy_file_range() on Linux (#8413)

copy_file_range() is a Linux-specific system call which allows
efficient copying between two file descriptors, eliminating the need
to transfer data from the kernel to userspace and back. For
networking file systems like NFS and Ceph, it even eliminates copying
data to the client, and local filesystems like Btrfs and XFS can
create shared extents.

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