Add Clone to Extensions::insert<T>

`http::Extensions::insert` requires `T: Clone` so we add it.

Author: allan2

tonic/src/extensions.rs

@@ -24,7 +24,7 @@ impl Extensions {
     /// If a extension of this type already existed, it will
     /// be returned.
     #[inline]
-    pub fn insert<T: Send + Sync + 'static>(&mut self, val: T) -> Option<T> {
+    pub fn insert<T: Send + Sync + Clone + 'static>(&mut self, val: T) -> Option<T> {
         self.inner.insert(val)
     }
 
@@ -95,3 +95,4 @@ impl GrpcMethod {
         self.method
     }
 }
+