[Virtio-fs] [virtiofsd-rs] MR opened: Allow using file handles instead of O_PATH FDs to reference inodes

[virtiofs-bot at sinrega.org]

Storing an `O_PATH` file descriptor in every `InodeData` means we have a lot of FDs open, which is sometimes bad.  This series adds an option (`--inode-file-handles`) that will make virtiofsd-rs attempt to generate a file handle for new inodes and store that instead of an FD.  When an FD is needed for a given inode, we open the handle.
---
https://gitlab.com/virtio-fs/virtiofsd-rs/-/merge_requests/26