[CP-beta]Update Android plugin templates for newer AGP (flutter#157100)

This pull request is created by [automatic cherry pick workflow](https://github.com/flutter/flutter/blob/main/docs/releases/Flutter-Cherrypick-Process.md#automatically-creates-a-cherry-pick-request)
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### Issue Link:
Part of flutter#156111

### Changelog Description:
Updates the Android plugin templates to use newer configurations that have better compatibility with recent versions of AGP.

### Impact Description:
Without this, plugins created by `flutter create` will have deprecation warnings out of the box for developers whose projects use new versions of AGP, and will eventually fail to compile without manual updates.

### Workaround:
Manually change the Java version after running `flutter create`

### Risk:
What is the risk level of this cherry-pick?

### Test Coverage:
Are you confident that your fix is well-tested by automated tests?

### Validation Steps:
1. `flutter create -t plugin some_plugin --platforms=android`
2. Update the example project to the latest version of AGP
3. Build

There should not be warnings about `source value 8 is obsolete` or `target value 8 is obsolete`.

Author: flutteractionsbot

packages/flutter_tools/templates/plugin/android-java.tmpl/build.gradle.tmpl

@@ -22,15 +22,13 @@ rootProject.allprojects {
 apply plugin: "com.android.library"
 
 android {
-    if (project.android.hasProperty("namespace")) {
-        namespace = "{{androidIdentifier}}"
-    }
+    namespace = "{{androidIdentifier}}"
 
     compileSdk = {{compileSdkVersion}}
 
     compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_1_8
-        targetCompatibility = JavaVersion.VERSION_1_8
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
     }
 
     defaultConfig {

packages/flutter_tools/templates/plugin/android-kotlin.tmpl/build.gradle.tmpl

@@ -25,19 +25,17 @@ apply plugin: "com.android.library"
 apply plugin: "kotlin-android"
 
 android {
-    if (project.android.hasProperty("namespace")) {
-        namespace = "{{androidIdentifier}}"
-    }
+    namespace = "{{androidIdentifier}}"
 
     compileSdk = {{compileSdkVersion}}
 
     compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_1_8
-        targetCompatibility = JavaVersion.VERSION_1_8
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
     }
 
     kotlinOptions {
-        jvmTarget = JavaVersion.VERSION_1_8
+        jvmTarget = JavaVersion.VERSION_11
     }
 
     sourceSets {

packages/flutter_tools/templates/plugin_ffi/android.tmpl/build.gradle.tmpl

@@ -25,9 +25,7 @@ rootProject.allprojects {
 apply plugin: "com.android.library"
 
 android {
-    if (project.android.hasProperty("namespace")) {
-        namespace = "{{androidIdentifier}}"
-    }
+    namespace = "{{androidIdentifier}}"
 
     // Bumping the plugin compileSdk version requires all clients of this plugin
     // to bump the version in their app.
@@ -55,8 +53,8 @@ android {
     }
 
     compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_1_8
-        targetCompatibility = JavaVersion.VERSION_1_8
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
     }
 
     defaultConfig {

packages/flutter_tools/test/commands.shard/permeable/create_test.dart

@@ -3231,6 +3231,54 @@ void main() {
     expect(buildGradleContent.contains('namespace = "com.bar.foo.flutter_project"'), true);
   });
 
+  testUsingContext('Android Java plugin sets explicit compatibility version', () async {
+    Cache.flutterRoot = '../..';
+
+    final CreateCommand command = CreateCommand();
+    final CommandRunner<void> runner = createTestCommandRunner(command);
+
+    await runner.run(<String>['create', '--no-pub',
+      '-t', 'plugin',
+      '--org', 'com.bar.foo',
+      '-a', 'java',
+      '--platforms=android',
+      projectDir.path]);
+
+    final File buildGradleFile = globals.fs.file('${projectDir.path}/android/build.gradle');
+
+    expect(buildGradleFile.existsSync(), true);
+
+    final String buildGradleContent = await buildGradleFile.readAsString();
+
+    expect(buildGradleContent.contains('sourceCompatibility = JavaVersion.VERSION_11'), true);
+    expect(buildGradleContent.contains('targetCompatibility = JavaVersion.VERSION_11'), true);
+  });
+
+  testUsingContext('Android Kotlin plugin sets explicit compatibility version', () async {
+    Cache.flutterRoot = '../..';
+
+    final CreateCommand command = CreateCommand();
+    final CommandRunner<void> runner = createTestCommandRunner(command);
+
+    await runner.run(<String>['create', '--no-pub',
+      '-t', 'plugin',
+      '--org', 'com.bar.foo',
+      '-a', 'kotlin',
+      '--platforms=android',
+      projectDir.path]);
+
+    final File buildGradleFile = globals.fs.file('${projectDir.path}/android/build.gradle');
+
+    expect(buildGradleFile.existsSync(), true);
+
+    final String buildGradleContent = await buildGradleFile.readAsString();
+
+    expect(buildGradleContent.contains('sourceCompatibility = JavaVersion.VERSION_11'), true);
+    expect(buildGradleContent.contains('targetCompatibility = JavaVersion.VERSION_11'), true);
+    // jvmTarget should be set to the same value.
+    expect(buildGradleContent.contains('jvmTarget = JavaVersion.VERSION_11'), true);
+  });
+
   testUsingContext('Flutter module Android project contains namespace', () async {
     const String moduleBuildGradleFilePath = '.android/build.gradle';
     const String moduleAppBuildGradleFlePath = '.android/app/build.gradle';