fix: perf issues in hot paths

1. no unused timers, wrap tracing calls to avoid stringifying
2. track graceful end of the call and avoid emitting 'cancelled' in such cases
3. remove validate calls in metadata on operations where it's not needed
4. refactor server session stream handlers into separate channelz enabled/disabled handlers
5. refactor message request logic - reduce amount of microtasks generated
6. improve sendStatus a little when there is no metadata involved

packages/grpc-js/src/call-stream.ts

@@ -97,6 +97,10 @@ export interface StatusObject {
   metadata: Metadata;
 }
 
+export type PartialStatusObject = Pick<StatusObject, 'code' | 'details'> & {
+  metadata: Metadata | null;
+}
+
 export const enum WriteFlags {
   BufferHint = 1,
   NoCompress = 2,