Use namespace for ReactAndroid and hermes-engine

Summary:
Our first party modules are still using `namespace`. This cleans this up.
The Manifest file for ReactAndroid is also not needed anymore. The one
from hermes-engine can also be removed from facebook/hermes in a separate diff.

Changelog:
[Internal] [Changed] - Use namespace for ReactAndroid and hermes-engine

Reviewed By: cipolleschi

Differential Revision: D43198514

fbshipit-source-id: d988cfa81ecc4484b6b2add4ae2c1d9376febc3e

ReactAndroid/build.gradle

@@ -417,6 +417,7 @@ task installArchives {
 android {
     buildToolsVersion = "33.0.0"
     compileSdkVersion 33
+    namespace "com.facebook.react"
 
     // Used to override the NDK path/version on internal CI or by allowing
     // users to customize the NDK path/version from their root project (e.g. for M1 support)

ReactAndroid/hermes-engine/build.gradle

@@ -119,6 +119,7 @@ def reactNativeArchitectures() {
 android {
     compileSdkVersion 31
     buildToolsVersion = "31.0.0"
+    namespace "com.facebook.hermes"
 
     // Used to override the NDK path/version on internal CI or by allowing
     // users to customize the NDK path/version from their root project (e.g. for M1 support)

ReactAndroid/src/main/AndroidManifest.xml

@@ -1,5 +0,0 @@
-<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.facebook.react">
-
-    <application />
-
-</manifest>