Moved package from AndroidManifest.xml into build.gradle namespace (#…

…5541)

Summary:
This is necessary because Google requires this in AGP version 8.

The code no longer works now that we're at version 8 of AGP. This is because AGP 8 requires that the package be changed to a namespace option in build.gradle.

## Changelog

The React Native module now works with Android Gradle Plugin version 8.

Pull Request resolved: #5541

Test Plan:
I imported this in my own React Native project, and I was getting a build failed: "Namespace not specified. Specify a namespace in the module's build file. See https://d.android.com/r/tools/upgrade-assistant/set-namespace for information about setting the namespace."

Then I made this one change and rebuilt my project. The build worked and my app ran correctly.

Reviewed By: LukeDefeo

Differential Revision: D55419610

Pulled By: passy

fbshipit-source-id: 5646172b14ab8a4ec6b6d3ffeb3b68c44e707883

react-native/react-native-flipper/android/build.gradle

@@ -48,6 +48,7 @@ def safeExtGet(prop, fallback) {
 apply plugin: 'com.android.library'
 
 android {
+    namespace 'com.facebook.flipper.reactnative'
     compileSdkVersion safeExtGet('compileSdkVersion', DEFAULT_COMPILE_SDK_VERSION)
     buildToolsVersion safeExtGet('buildToolsVersion', DEFAULT_BUILD_TOOLS_VERSION)
     defaultConfig {