vmm: disk resize infrastructure

Add basic infrastructure so resize events are
propagated to the underlying disk implementation.

On-behalf-of: SAP thomas.prescher@sap.com
Signed-off-by: Thomas Prescher <thomas.prescher@cyberus-technology.de>

fuzz/fuzz_targets/http_api.rs

@@ -108,6 +108,10 @@ impl RequestHandler for StubApiRequestHandler {
         Ok(())
     }
 
+    fn vm_resize_disk(&mut self, _: String, _: u64) -> Result<(), VmError> {
+        Ok(())
+    }
+
     #[cfg(target_arch = "x86_64")]
     fn vm_coredump(&mut self, _: &str) -> Result<(), VmError> {
         Ok(())