Configure Java toolchains only when executing App configuration (#40757)

Summary:
Fix #40560

## Changelog:

[ANDROID] [FIXED] - Ensure that `configureJavaToolChains` is only executed once during configuration

Pull Request resolved: #40757

Test Plan:
- Create a fresh `[email protected]` project
- Install `react-native-webview`
- Apply [this patch](https://github.com/react-native-webview/react-native-webview/pull/3175/files) for `react-native-webview` (caused by another issue #40559)
- Edit `android/gradle.properties` and set `newArchEnabled` to true
- Build application
- (Expected) Application fail to build
- Apply this PR
- (Expected) Application build successfully

**Additional explanation:**

According to the implementation of `configureJavaToolChains`, all the subprojects (both the app and the libraries) will have their toolchains setup in one execution of the method. Therefore, it is okay for the method to be invoked only when configuring the plugin for the app.

On the other hand, invoking the method for more than one time will cause the issue stated in #40560.

Reviewed By: cipolleschi

Differential Revision: D50361871

Pulled By: cortinico

fbshipit-source-id: bd5e18df97988122788d0482dba954e517a0cb5c

packages/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/ReactPlugin.kt

@@ -68,6 +68,7 @@ class ReactPlugin : Plugin<Project> {
       configureBuildConfigFieldsForApp(project, extension)
       configureDevPorts(project)
       configureBackwardCompatibilityReactMap(project)
+      configureJavaToolChains(project)
 
       project.extensions.getByType(AndroidComponentsExtension::class.java).apply {
         onVariants(selector().all()) { variant ->
@@ -78,13 +79,10 @@ class ReactPlugin : Plugin<Project> {
     }
 
     // Library Only Configuration
+    configureBuildConfigFieldsForLibraries(project)
     project.pluginManager.withPlugin("com.android.library") {
       configureCodegen(project, extension, rootExtension, isLibrary = true)
     }
-
-    // Library and App Configurations
-    configureJavaToolChains(project)
-    configureBuildConfigFieldsForLibraries(project)
   }
 
   private fun checkJvmVersion(project: Project) {