virtio-devices: Remove virtio-block synchronous implementation

Now that both synchronous and asynchronous backends rely on the
asynchronous version of virtio-block (namely BlockIoUring), we can
get rid of the synchronous version (namely Block).

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

fuzz/Cargo.toml

@@ -9,6 +9,7 @@ edition = "2018"
 cargo-fuzz = true
 
 [dependencies]
+block_util = { path = "../block_util" }
 libc = "0.2.72"
 libfuzzer-sys = "0.3"
 qcow = { path = "../qcow" }