stream: deprecate piping to emitters without prependListener

The prependListener method has been available on EventEmitter since
Node.js v6.0.0 (April 2016). The internal fallback code that manually
manipulates the _events object was intended for pre-v6 compatibility.

This adds a runtime deprecation warning (DEP0205) when piping to an
EventEmitter that lacks the prependListener method. The fallback
behavior is preserved for now but will be removed in a future version.

PR-URL: https://github.com/nodejs/node/pull/XXXXX
Refs: https://github.com/nodejs/node/issues/XXXXX

Author: karan-lrn

doc/api/deprecations.md

@@ -4563,6 +4563,22 @@ that have proven unresolveable. See [caveats of asynchronous customization hooks
 `module.registerHooks()` as soon as possible as `module.register()` will be
 removed in a future version of Node.js.
 
+### DEP0206: Piping to emitters without `prependListener`
+
+<!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/62435
+    description: Runtime deprecation.
+-->
+
+Type: Runtime
+
+Piping to an EventEmitter that does not have a `prependListener` method is
+deprecated. The `prependListener` method has been available on EventEmitter
+since Node.js v6.0.0. The internal fallback code that manually manipulates
+the `_events` object will be removed in a future version.
+
 [DEP0142]: #dep0142-repl_builtinlibs
 [NIST SP 800-38D]: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf
 [RFC 6066]: https://tools.ietf.org/html/rfc6066#section-3

lib/internal/streams/legacy.js

@@ -122,7 +122,7 @@ function prependListener(emitter, event, fn) {
       'Piping to an EventEmitter without a prependListener method is deprecated. ' +
       'The emitter should have a prependListener method.',
       'DeprecationWarning',
-      'DEP0205',
+      'DEP0206',
     );
     emittedPrependListenerDeprecation = true;
   }

test/parallel/test-event-emitter-prepend.js

@@ -42,7 +42,7 @@ common.expectWarning(
   'DeprecationWarning',
   'Piping to an EventEmitter without a prependListener method is deprecated. ' +
   'The emitter should have a prependListener method.',
-  'DEP0205',
+  'DEP0206',
 );
 
 const w = new Writable();

test/parallel/test-stream-events-prepend.js

@@ -24,7 +24,7 @@ common.expectWarning(
   'DeprecationWarning',
   'Piping to an EventEmitter without a prependListener method is deprecated. ' +
   'The emitter should have a prependListener method.',
-  'DEP0205',
+  'DEP0206',
 );
 
 const w = new Writable();