node:test add Subtest to tap protocol output

just used tap-mocha-reporter to compare how output will look visually and saw it was missing

Author: MoLow

lib/internal/test_runner/tap_stream.js

@@ -71,6 +71,10 @@ class TapStream extends Readable {
     return `TODO${reason ? ` ${tapEscape(reason)}` : ''}`;
   }
 
+  subTest(indent, name) {
+    this.#tryPush(`${indent}# Subtest: ${tapEscape(name)}\n`);
+  }
+
   details(indent, duration, error) {
     let details = `${indent}  ---\n`;
 

lib/internal/test_runner/test.js

@@ -280,6 +280,7 @@ class Test extends AsyncResource {
   }
 
   start() {
+    this.reporter.subTest(this.indent, this.name);
     // If there is enough available concurrency to run the test now, then do
     // it. Otherwise, return a Promise to the caller and mark the test as
     // pending for later execution.