Upgrade module template AGP version (#151675)

Follow up to flutter/flutter#151433.

Author: gmackall

packages/flutter_tools/lib/src/android/gradle_utils.dart

@@ -28,7 +28,7 @@ import 'android_sdk.dart';
 // Please see the README before changing any of these values.
 const String templateDefaultGradleVersion = '8.3';
 const String templateAndroidGradlePluginVersion = '8.1.0';
-const String templateAndroidGradlePluginVersionForModule = '7.3.0';
+const String templateAndroidGradlePluginVersionForModule = '8.1.0';
 const String templateKotlinGradlePluginVersion = '1.8.22';
 
 // The Flutter Gradle Plugin is only applied to app projects, and modules that

packages/flutter_tools/templates/module/android/library_new_embedding/Flutter.tmpl/build.gradle.tmpl

@@ -47,6 +47,22 @@ android {
     }
 }
 
+android.buildTypes.all {buildType ->
+    if (!android.productFlavors.isEmpty()) {
+        android.productFlavors.all{productFlavor ->
+            android.publishing.singleVariant(productFlavor.name + buildType.name.capitalize()) {
+                withSourcesJar()
+                withJavadocJar()
+            }
+        }
+    } else {
+        android.publishing.singleVariant(buildType.name) {
+            withSourcesJar()
+            withJavadocJar()
+        }
+    }
+}
+
 flutter {
     source = "../.."
 }