feat: "rejectionhandled" Web event and "rejectionHandled" Node event (#21875)

This commit adds support for "rejectionhandled" Web Event and
"rejectionHandled" Node event.

```js
import process from "node:process";

process.on("rejectionHandled", (promise) => {
  console.log("rejectionHandled", reason, promise);
});

window.addEventListener("rejectionhandled", (event) => {
  console.log("rejectionhandled", event.reason, event.promise);
});
```

---------

Co-authored-by: Matt Mastracci <matthew@mastracci.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/runtime/js/99_main.js b/runtime/js/99_main.js
index 4644d2d08..6c5ca3b59 100644
--- a/runtime/js/99_main.js
+++ b/runtime/js/99_main.js
@@ -344,6 +344,8 @@ function runtimeStart(
 }
 
 core.setUnhandledPromiseRejectionHandler(processUnhandledPromiseRejection);
+core.setHandledPromiseRejectionHandler(processRejectionHandled);
+
 // Notification that the core received an unhandled promise rejection that is about to
 // terminate the runtime. If we can handle it, attempt to do so.
 function processUnhandledPromiseRejection(promise, reason) {
@@ -377,6 +379,20 @@ function processUnhandledPromiseRejection(promise, reason) {
   return false;
 }
 
+function processRejectionHandled(promise, reason) {
+  const rejectionHandledEvent = new event.PromiseRejectionEvent(
+    "rejectionhandled",
+    { promise, reason },
+  );
+
+  // Note that the handler may throw, causing a recursive "error" event
+  globalThis_.dispatchEvent(rejectionHandledEvent);
+
+  if (typeof internals.nodeProcessRejectionHandledCallback !== "undefined") {
+    internals.nodeProcessRejectionHandledCallback(rejectionHandledEvent);
+  }
+}
+
 let hasBootstrapped = false;
 // Delete the `console` object that V8 automaticaly adds onto the global wrapper
 // object on context creation. We don't want this console object to shadow the