Add @DoNotStrip to method called from cpp in bridgeless mode

Summary:
I hit a crash when testing bridgeless mode in a release build:

Error: Exception in HostFunction: java.lang.NoSuchMethodError: no non-static method "Lcom/facebook/react/modules/core/JavaTimerManager;.createTimer(IJZ)V"

It turns out that `JavaTimerManager.createTimer()` is getting stripped from release builds because it's not referenced in Java at all. Adding `DoNotStrip` annotation to keep it around. The other methods in JavaTimerManager don't need this because they're referenced by TimingModule - this is the only method that's only used directly from C++ by bridgeless mode.

Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D19655519

fbshipit-source-id: 8b9862475986bb84b12d81f73f677cc2e4860c67

ReactAndroid/src/main/java/com/facebook/react/modules/core/JavaTimerManager.java

@@ -9,6 +9,7 @@ package com.facebook.react.modules.core;
 
 import android.util.SparseArray;
 import androidx.annotation.Nullable;
+import com.facebook.proguard.annotations.DoNotStrip;
 import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.ReactApplicationContext;
 import com.facebook.react.bridge.UiThreadUtil;
@@ -293,6 +294,7 @@ public class JavaTimerManager {
    * @param delay The time in ms before the callback should be invoked.
    * @param repeat Whether the timer should be repeated (used for setInterval).
    */
+  @DoNotStrip
   public void createTimer(final int callbackID, final long delay, final boolean repeat) {
     long initialTargetTime = SystemClock.nanoTime() / 1000000 + delay;
     Timer timer = new Timer(callbackID, initialTargetTime, (int) delay, repeat);