Implement Clone for capnp::capability::Client

It is trivial to implement and codegen already does the same code snippet
to clone the client.

So I implemented Clone and changed codegen to use that instead.

Author: griff

capnp/src/capability.rs

@@ -413,6 +413,15 @@ impl FromClientHook for Client {
     }
 }
 
+#[cfg(feature = "alloc")]
+impl Clone for Client {
+    fn clone(&self) -> Self {
+        Self {
+            hook: self.hook.add_ref(),
+        }
+    }
+}
+
 /// The return value of Server::dispatch_call().
 #[cfg(feature = "alloc")]
 pub struct DispatchCallResult {

capnpc/src/codegen.rs

@@ -2810,13 +2810,18 @@ fn generate_node(
                 line("}"),
             ]));
 
-            mod_interior.push(
-                Branch(vec![
-                    Line(format!("impl {bracketed_params} Clone for Client{bracketed_params} {{")),
-                    indent(line("fn clone(&self) -> Self {")),
-                    indent(indent(Line(fmt!(ctx,"Self {{ client: {capnp}::capability::Client::new(self.client.hook.add_ref()), {} }}", params.phantom_data_value)))),
-                    indent(line("}")),
-                    line("}")]));
+            mod_interior.push(Branch(vec![
+                Line(format!(
+                    "impl {bracketed_params} Clone for Client{bracketed_params} {{"
+                )),
+                indent(line("fn clone(&self) -> Self {")),
+                indent(indent(Line(format!(
+                    "Self {{ client: self.client.clone(), {} }}",
+                    params.phantom_data_value
+                )))),
+                indent(line("}")),
+                line("}"),
+            ]));
 
             mod_interior.push(Branch(vec![
                 Line(format!(