block: Add punch_hole and write_zeroes to AsyncIo trait

Add punch_hole() and write_zeroes() methods to the AsyncIo trait
with stub implementations for all backends. These will be used to
support DISCARD and WRITE_ZEROES operations.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>

block/src/raw_async_aio.rs

@@ -161,4 +161,16 @@ impl AsyncIo for RawFileAsyncAio {
             Some((events[0].data, events[0].res as i32))
         }
     }
+
+    fn punch_hole(&mut self, _offset: u64, _length: u64, _user_data: u64) -> AsyncIoResult<()> {
+        Err(AsyncIoError::PunchHole(std::io::Error::other(
+            "punch_hole not supported with AIO backend",
+        )))
+    }
+
+    fn write_zeroes(&mut self, _offset: u64, _length: u64, _user_data: u64) -> AsyncIoResult<()> {
+        Err(AsyncIoError::WriteZeroes(std::io::Error::other(
+            "write_zeroes not supported with AIO backend",
+        )))
+    }
 }