Do not store .cpp/.h files inside src/main/java - uimanager

Summary:
Currently we expose native code (.h, .cpp) inside the src/main/java folder.

This is making impossible for users on New Architecture to open the project
inside Android Studio.

The problem is that the src/main/java is reserved to Java/Kotlin sources only.

AGP 7.2 also removed support for mixed source roots:
https://developer.android.com/studio/releases/gradle-plugin#duplicate-content-roots

This is essentially forcing users to write Java code without any autocompletion
as all the React Native Java classes are considered C++ files.

I'm addressing this issue folder by folder by moving them
from ReactAndroid/src/main/java/com/facebook/... to ReactAndroid/src/main/jni/react/...

This is the diff for uimanager

Changelog:
[Internal] [Changed] - Do not store .cpp/.h files inside src/main/java - uimanager

Reviewed By: dmitryrykun

Differential Revision: D38656400

fbshipit-source-id: f52487160fa6c05ec382842e2a6125a5c4cb1e86

ReactAndroid/src/main/java/com/facebook/react/uimanager/BUCK

@@ -76,7 +76,6 @@ rn_android_library(
         react_native_target("java/com/facebook/debug/tags:tags"),
         react_native_target("java/com/facebook/debug/holder:holder"),
         react_native_target("java/com/facebook/react/bridge:bridge"),
-        react_native_target("java/com/facebook/react/uimanager/jni:jni"),
         react_native_target("java/com/facebook/react/common:common"),
         react_native_target("java/com/facebook/react/common/mapbuffer:mapbuffer"),
         react_native_target("java/com/facebook/react/config:config"),
@@ -86,6 +85,7 @@ rn_android_library(
         react_native_target("java/com/facebook/react/touch:touch"),
         react_native_target("java/com/facebook/react/uimanager/annotations:annotations"),
         react_native_target("java/com/facebook/react/uimanager/util:util"),
+        react_native_target("jni/react/uimanager:jni"),
         react_native_target("res:uimanager"),
     ],
     exported_deps = [

ReactAndroid/src/main/jni/CMakeLists.txt

@@ -98,7 +98,7 @@ add_react_android_subdir(src/main/jni/react/jni)
 add_react_android_subdir(src/main/jni/react/reactperflogger)
 add_react_android_subdir(src/main/java/com/facebook/react/jscexecutor)
 add_react_android_subdir(src/main/java/com/facebook/react/turbomodule/core/jni)
-add_react_android_subdir(src/main/java/com/facebook/react/uimanager/jni)
+add_react_android_subdir(src/main/jni/react/uimanager)
 add_react_android_subdir(src/main/java/com/facebook/react/common/mapbuffer/jni)
 add_react_android_subdir(src/main/java/com/facebook/react/fabric/jni)
 add_react_android_subdir(src/main/java/com/facebook/react/modules/blob/jni)