Bump Gradle plugin Kotlin API version from 2.0 to 2.1

Summary:
Kotlin 2.3 deprecated API version 2.0, so compiling the Gradle plugin modules with warnings as errors fails with "API version 2.0 is deprecated" in `:gradle-plugin:shared:compileKotlin`. Bump `apiVersion` to `KOTLIN_2_1` in all four gradle-plugin build files, matching how the previous Kotlin upgrade moved it from 1.9 to 2.0.

Gradle 9, which React Native requires, embeds a Kotlin 2.2 runtime, so the plugin stays loadable on every supported Gradle version.

Changelog:
[Android][Changed] - Bumped the Gradle plugin's minimum Kotlin API version to 2.1

Differential Revision: D127831836

Author: Abbondanzo

packages/gradle-plugin/react-native-gradle-plugin/build.gradle.kts

@@ -63,7 +63,7 @@ kotlin { jvmToolchain(17) }
 
 tasks.withType<KotlinCompile>().configureEach {
   compilerOptions {
-    apiVersion.set(KotlinVersion.KOTLIN_2_0)
+    apiVersion.set(KotlinVersion.KOTLIN_2_1)
     // See comment above on JDK 11 support
     jvmTarget.set(JvmTarget.JVM_11)
     allWarningsAsErrors.set(

packages/gradle-plugin/settings-plugin/build.gradle.kts

@@ -53,7 +53,7 @@ kotlin { jvmToolchain(17) }
 
 tasks.withType<KotlinCompile>().configureEach {
   compilerOptions {
-    apiVersion.set(KotlinVersion.KOTLIN_2_0)
+    apiVersion.set(KotlinVersion.KOTLIN_2_1)
     // See comment above on JDK 11 support
     jvmTarget.set(JvmTarget.JVM_11)
     allWarningsAsErrors.set(

packages/gradle-plugin/shared-testutil/build.gradle.kts

@@ -24,7 +24,7 @@ kotlin { jvmToolchain(17) }
 
 tasks.withType<KotlinCompile>().configureEach {
   compilerOptions {
-    apiVersion.set(KotlinVersion.KOTLIN_2_0)
+    apiVersion.set(KotlinVersion.KOTLIN_2_1)
     // See comment above on JDK 11 support
     jvmTarget.set(JvmTarget.JVM_11)
     allWarningsAsErrors.set(

packages/gradle-plugin/shared/build.gradle.kts

@@ -30,7 +30,7 @@ kotlin { jvmToolchain(17) }
 
 tasks.withType<KotlinCompile>().configureEach {
   compilerOptions {
-    apiVersion.set(KotlinVersion.KOTLIN_2_0)
+    apiVersion.set(KotlinVersion.KOTLIN_2_1)
     // See comment above on JDK 11 support
     jvmTarget.set(JvmTarget.JVM_11)
     allWarningsAsErrors.set(