test_runner: disable highWatermark on TestsStream

The default highWatermark of 16 on the TestsStream class can
have a substantial impact on reporting performance. This commit
sets the TestsStream highWatermark to a very large value and
lets the destination streams (which are more likely to have
meaningful highWatermarks) handle backpressure.

PR-URL: #52287
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

lib/internal/test_runner/tests_stream.js

@@ -2,6 +2,7 @@
 const {
   ArrayPrototypePush,
   ArrayPrototypeShift,
+  NumberMAX_SAFE_INTEGER,
   Symbol,
 } = primordials;
 const Readable = require('internal/streams/readable');
@@ -12,7 +13,11 @@ class TestsStream extends Readable {
   #canPush;
 
   constructor() {
-    super({ __proto__: null, objectMode: true });
+    super({
+      __proto__: null,
+      objectMode: true,
+      highWaterMark: NumberMAX_SAFE_INTEGER,
+    });
     this.#buffer = [];
     this.#canPush = true;
   }