Add benchmark for host component class variants (facebook#48450)

Summary:

Changelog: [internal]

This implements a basic benchmark to compare `ReactFabricHostComponent` and `ReactNativeElement` (legacy and DOM implementations for native component instances).

Reviewed By: rshest

Differential Revision: D66698546

packages/react-native/Libraries/ReactNative/ReactFabricPublicInstance/__tests__/ReactFabricPublicInstance-benchmark-itest.js

@@ -0,0 +1,61 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+import '../../../Core/InitializeCore.js';
+import type {
+  InternalInstanceHandle,
+  ViewConfig,
+} from '../../../Renderer/shims/ReactNativeTypes';
+
+import ReactNativeElement from '../../../../src/private/webapis/dom/nodes/ReactNativeElement';
+import ReactFabricHostComponent from '../../../ReactNative/ReactFabricPublicInstance/ReactFabricHostComponent';
+import {benchmark} from '@react-native/fantom';
+import nullthrows from 'nullthrows';
+
+// Create fake parameters for the class.
+const tag = 11;
+const viewConfig: ViewConfig = {
+  uiViewClassName: 'test',
+  validAttributes: {
+    style: {},
+  },
+};
+// $FlowExpectedError[incompatible-type]
+const internalInstanceHandle: InternalInstanceHandle = {};
+
+benchmark
+  .suite('ReactNativeElement vs. ReactFabricHostComponent')
+  .add('ReactNativeElement', () => {
+    // eslint-disable-next-line no-new
+    new ReactNativeElement(tag, viewConfig, internalInstanceHandle);
+  })
+  .add('ReactFabricHostComponent', () => {
+    // eslint-disable-next-line no-new
+    new ReactFabricHostComponent(tag, viewConfig, internalInstanceHandle);
+  })
+  .verify(([modernImplResults, legacyImplResults]) => {
+    const minMedian = Math.min(
+      nullthrows(modernImplResults.latency.p50),
+      nullthrows(legacyImplResults.latency.p50),
+    );
+    const maxMedian = Math.max(
+      nullthrows(modernImplResults.latency.p50),
+      nullthrows(legacyImplResults.latency.p50),
+    );
+
+    const medianDifferencePercent = ((maxMedian - minMedian) / minMedian) * 100;
+    console.log(
+      `Difference in p50 values between ReactFabricHostComponent and ReactNativeElement is ${medianDifferencePercent.toFixed(2)}%`,
+    );
+
+    // No implementation should be more than 25% slower than the other.
+    expect(medianDifferencePercent).toBeLessThan(25);
+  });