fix(android): log missing generated setter at debug level, not warn

[franruiztech]

Summary:

ViewManagerPropertyUpdater.findGeneratedSetter looks up a <class>$$PropsSetter class by reflection and, when it does not exist, logs Could not find generated setter for class ... at warn level and falls back to reflection over the @ReactProp methods (FallbackViewManagerSetter / FallbackShadowNodeSetter).

The annotation processor that generated those setters (ReactPropertyProcessor) was removed in #49811 (first released in 0.80). Since then no view manager in React Native has a generated setter, so the fallback is the normal path and the warning is printed once per view manager and shadow node class on every app run (71 lines in a typical app start on 0.85.3). It is not an error and there is nothing the app developer can do about it. Users have reported it as logcat noise several times (#29864, #31416, #45211), and it is easy to mistake for the cause of an unrelated crash.

This changes the log call from FLog.w to FLog.d. The lookup itself is kept, because a library can still ship a generated setter, and the message stays available for anyone debugging prop setup. It does not touch FLog configuration.

Changelog:

[ANDROID] [FIXED] - Do not log "Could not find generated setter" at warn level; the reflection fallback is the expected path

Test Plan:

Added ViewManagerPropertyUpdaterTest: it resolves the native props of a view manager that has no generated setter, with FLog mocked, and checks that the props are still found through the fallback and that FLog.w is not called.

Ran it with ./gradlew :packages:react-native:ReactAndroid:testDebugUnitTest --tests com.facebook.react.uimanager.ViewManagerPropertyUpdaterTest: 1 test, passes. With the call put back to FLog.w (and nothing else changed) the same run fails with NeverWantedButInvoked for FLog.w(String, String), reporting the Could not find generated setter for class ...ViewManagerWithoutGeneratedSetter call from findGeneratedSetter. The test follows the same mockStatic(FLog) pattern as the neighbouring tests.

I also compiled the changed ViewManagerPropertyUpdater against the 0.85.3 react-android release AAR and replaced the classes in it; javap -c shows the call site now targets FLog.d and nothing else in the class changed.

On an Android 9 (API 28) x86_64 emulator, with a release build of an app on 0.85.3 (R8, Hermes, New Architecture), I ran the same scripted flow twice: login, five tabs, a list with about 20 remote logos, a company detail screen, and a cold restart. I counted the matching logcat lines.

react-android	Could not find generated setter
stock 0.85.3	142 lines
0.85.3 with this patch (and the one for the Fresco rounding warning)	0 lines

Stock 0.85.3 on API 26, 31, 33 and 36 gives 141 to 142 lines for the same flow. The patched build was run on API 28 and API 34 (Android 14), with 0 lines on both, and it did not crash.

The patched react-android was built by recompiling the changed classes and replacing them in the official 0.85.3 AAR, not with a full Gradle build of ReactAndroid.