feat(tvix/store/fs): Add support for virtiofs backend

This adds a virtiofs daemon implementation which hooks into the existing
tvix-store filesystem implementation that is used for FUSE.

This allows adding the filesystem to a microvm without having to set up
FUSE inside the guest.

Change-Id: If80c36c9657f2289853e8d9a364bf4f1f7b7559c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9344
Autosubmit: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

tvix/store/src/fs/mod.rs

@@ -5,6 +5,9 @@ mod inodes;
 #[cfg(feature = "fuse")]
 pub mod fuse;
 
+#[cfg(feature = "virtiofs")]
+pub mod virtiofs;
+
 #[cfg(test)]
 mod tests;