vmm: add HTTP API endpoints for generic vhost-user

This includes OpenAPI schemas.

Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>

fuzz/fuzz_targets/http_api.rs

@@ -168,6 +168,7 @@ impl RequestHandler for StubApiRequestHandler {
                 },
                 balloon: None,
                 fs: None,
+                generic_vhost_user: None,
                 pmem: None,
                 serial: ConsoleConfig {
                     file: None,
@@ -254,6 +255,13 @@ impl RequestHandler for StubApiRequestHandler {
         Ok(None)
     }
 
+    fn vm_add_generic_vhost_user(
+        &mut self,
+        _: GenericVhostUserConfig,
+    ) -> Result<Option<Vec<u8>>, VmError> {
+        Ok(None)
+    }
+
     fn vm_add_pmem(&mut self, _: PmemConfig) -> Result<Option<Vec<u8>>, VmError> {
         Ok(None)
     }