Mark SingleThreadAsserter as @LegacyArchitecture (#50307)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/50307

Mark SingleThreadAsserter as LegacyArchitecture

changelog: [internal] internal

Reviewed By: alanleedev

Differential Revision: D71820293

fbshipit-source-id: a974ee65b2659028d14f73504f73db2b3ae63f70

packages/react-native/ReactAndroid/api/ReactAndroid.api

@@ -1776,11 +1776,6 @@ public abstract interface class com/facebook/react/common/ShakeDetector$ShakeLis
 	public abstract fun onShake ()V
 }
 
-public final class com/facebook/react/common/SingleThreadAsserter {
-	public fun <init> ()V
-	public final fun assertNow ()V
-}
-
 public abstract interface class com/facebook/react/common/SurfaceDelegate {
 	public abstract fun createContentView (Ljava/lang/String;)V
 	public abstract fun destroyContentView ()V

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/common/SingleThreadAsserter.kt

@@ -1,23 +0,0 @@
-/*
- * 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.
- */
-
-package com.facebook.react.common
-
-import com.facebook.infer.annotation.Assertions
-
-/** Simple class for asserting that operations only run on a single thread. */
-public class SingleThreadAsserter {
-  private var thread: Thread? = null
-
-  public fun assertNow() {
-    val currentThread = Thread.currentThread()
-    if (thread == null) {
-      thread = currentThread
-    }
-    Assertions.assertCondition(thread == currentThread)
-  }
-}

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/ShadowNodeRegistry.kt

@@ -10,7 +10,7 @@ package com.facebook.react.uimanager
 import android.util.SparseArray
 import android.util.SparseBooleanArray
 import android.view.View
-import com.facebook.react.common.SingleThreadAsserter
+import com.facebook.infer.annotation.Assertions
 import com.facebook.react.common.annotations.internal.LegacyArchitecture
 import com.facebook.react.common.annotations.internal.LegacyArchitectureLogLevel
 import com.facebook.react.common.annotations.internal.LegacyArchitectureLogger
@@ -88,4 +88,16 @@ internal class ShadowNodeRegistry {
           "ShadowNodeRegistry", LegacyArchitectureLogLevel.WARNING)
     }
   }
+
+  inner class SingleThreadAsserter {
+    private var thread: Thread? = null
+
+    public fun assertNow() {
+      val currentThread = Thread.currentThread()
+      if (thread == null) {
+        thread = currentThread
+      }
+      Assertions.assertCondition(thread == currentThread)
+    }
+  }
 }