vmm: add configuration for network offloading features

Add new configuration for offloading features, including
Checksum/TSO/UFO, and set these offloading features as
enabled by default.

Fixes: #4792.

Signed-off-by: Yong He <alexyonghe@tencent.com>

fuzz/fuzz_targets/net.rs

@@ -76,6 +76,9 @@ fuzz_target!(|bytes| {
         None,
         EventFd::new(EFD_NONBLOCK).unwrap(),
         None,
+        true,
+        true,
+        true,
     )
     .unwrap();