Migrate JavaScriptContextHolder & JavaScriptExecutor to Kotlin (#49909)

Summary:
Migrate com.facebook.react.bridge JavaScriptContextHolder & JavaScriptExecutor to Kotlin.

In this PR I also marked the return of HermesExecutor.initHybridDefaultConfig as non-nullable to keep the conversion without logic changes. I checked that this was changed unintentionally to nullable in 12e321daf0 but I think it was not supposed to be.

## Changelog:

[INTERNAL] - Migrate com.facebook.react.bridge JavaScriptContextHolder & JavaScriptExecutor to Kotlin

Pull Request resolved: https://github.com/facebook/react-native/pull/49909

Test Plan:
```bash
yarn test-android
yarn android
```

Reviewed By: javache

Differential Revision: D70871012

Pulled By: Abbondanzo

fbshipit-source-id: 1c15927056baf166e520e896e92bebf664fa0229

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

@@ -892,10 +892,10 @@ public final class com/facebook/react/bridge/JavaOnlyMap$Companion {
 	public final fun of ([Ljava/lang/Object;)Lcom/facebook/react/bridge/JavaOnlyMap;
 }
 
-public class com/facebook/react/bridge/JavaScriptContextHolder {
+public final class com/facebook/react/bridge/JavaScriptContextHolder {
 	public fun <init> (J)V
-	public fun clear ()V
-	public fun get ()J
+	public final fun clear ()V
+	public final fun get ()J
 }
 
 public abstract class com/facebook/react/bridge/JavaScriptExecutor {

packages/react-native/ReactAndroid/src/main/java/com/facebook/hermes/reactexecutor/HermesExecutor.kt

@@ -42,7 +42,7 @@ public class HermesExecutor internal constructor(enableDebugger: Boolean, debugg
     private external fun initHybridDefaultConfig(
         enableDebugger: Boolean,
         debuggerName: String
-    ): HybridData?
+    ): HybridData
 
     @DoNotStrip
     @JvmStatic
@@ -50,6 +50,6 @@ public class HermesExecutor internal constructor(enableDebugger: Boolean, debugg
         enableDebugger: Boolean,
         debuggerName: String,
         heapSizeMB: Long
-    ): HybridData?
+    ): HybridData
   }
 }

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/JavaScriptContextHolder.kt

@@ -5,29 +5,21 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-package com.facebook.react.bridge;
+package com.facebook.react.bridge
 
-import androidx.annotation.GuardedBy;
+import androidx.annotation.GuardedBy
 
 /**
  * Wrapper for JavaScriptContext native pointer. CatalystInstanceImpl creates this on demand, and
  * will call clear() before destroying the VM. People who need the raw JavaScriptContext pointer can
  * synchronize on this wrapper object to guarantee that it will not be destroyed.
  */
-public class JavaScriptContextHolder {
-  @GuardedBy("this")
-  private long mContext;
+public class JavaScriptContextHolder
+public constructor(@field:GuardedBy("this") private var context: Long) {
+  @GuardedBy("this") public fun get(): Long = context
 
-  public JavaScriptContextHolder(long context) {
-    mContext = context;
-  }
-
-  @GuardedBy("this")
-  public long get() {
-    return mContext;
-  }
-
-  public synchronized void clear() {
-    mContext = 0;
+  @Synchronized
+  public fun clear() {
+    context = 0
   }
 }

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/JavaScriptExecutor.java

@@ -1,31 +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.bridge;
-
-import com.facebook.jni.HybridData;
-import com.facebook.proguard.annotations.DoNotStrip;
-
-@DoNotStrip
-public abstract class JavaScriptExecutor {
-  private final HybridData mHybridData;
-
-  protected JavaScriptExecutor(HybridData hybridData) {
-    mHybridData = hybridData;
-  }
-
-  /**
-   * Close this executor and cleanup any resources that it was using. No further calls are expected
-   * after this. TODO mhorowitz: This may no longer be used; check and delete if possible.
-   */
-  public void close() {
-    mHybridData.resetNative();
-  }
-
-  /** Returns the name of the executor, identifying the underlying runtime. */
-  public abstract String getName();
-}

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/JavaScriptExecutor.kt

@@ -0,0 +1,30 @@
+/*
+ * 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.bridge
+
+import com.facebook.jni.HybridData
+import com.facebook.proguard.annotations.DoNotStripAny
+
+@DoNotStripAny
+public abstract class JavaScriptExecutor
+protected constructor(
+    // fbjni looks for the exact name "mHybridData":
+    // https://github.com/facebookincubator/fbjni/blob/7b7efda0d49b956acf1d3307510e3c73fc55b404/cxx/fbjni/detail/Hybrid.h#L310
+    @Suppress("NoHungarianNotation") private val mHybridData: HybridData
+) {
+  /**
+   * Close this executor and cleanup any resources that it was using. No further calls are expected
+   * after this. TODO mhorowitz: This may no longer be used; check and delete if possible.
+   */
+  public open fun close() {
+    mHybridData.resetNative()
+  }
+
+  /** Returns the name of the executor, identifying the underlying runtime. */
+  public abstract fun getName(): String
+}