Upgrade to Kotlin 1.8.20

Closes gh-34879

gradle.properties

@@ -4,7 +4,7 @@ org.gradle.caching=true
 org.gradle.parallel=true
 org.gradle.jvmargs=-Xmx2g -Dfile.encoding=UTF-8
 
-kotlinVersion=1.8.10
+kotlinVersion=1.8.20
 tomcatVersion=10.1.7
 nativeBuildToolsVersion=0.9.20
 

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/plugin/KotlinPluginActionIntegrationTests.java

@@ -83,7 +83,7 @@ class KotlinPluginActionIntegrationTests {
 			assertThat(configured).containsExactly("help");
 		}
 		else {
-			assertThat(configured).containsExactlyInAnyOrder("help", "clean", "compileKotlin", "compileTestKotlin");
+			assertThat(configured).containsExactlyInAnyOrder("help", "clean");
 		}
 	}
 

spring-boot-project/spring-boot-tools/spring-boot-gradle-test-support/src/main/java/org/springframework/boot/testsupport/gradle/testkit/GradleBuild.java

@@ -49,8 +49,9 @@ import org.gradle.testkit.runner.GradleRunner;
 import org.gradle.util.GradleVersion;
 import org.jetbrains.kotlin.gradle.model.KotlinProject;
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilerPluginSupportPlugin;
-import org.jetbrains.kotlin.gradle.plugin.KotlinPlugin;
+import org.jetbrains.kotlin.gradle.plugin.KotlinPlatformJvmPlugin;
 import org.jetbrains.kotlin.project.model.LanguageSettings;
+import org.jetbrains.kotlin.tooling.core.KotlinToolingVersion;
 import org.tomlj.Toml;
 
 import org.springframework.asm.ClassVisitor;
@@ -118,7 +119,9 @@ public class GradleBuild {
 				new File(pathOfJarContaining(DependencyManagementPlugin.class)),
 				new File(pathOfJarContaining("org.jetbrains.kotlin.cli.common.PropertiesKt")),
 				new File(pathOfJarContaining("org.jetbrains.kotlin.compilerRunner.KotlinLogger")),
-				new File(pathOfJarContaining(KotlinPlugin.class)), new File(pathOfJarContaining(KotlinProject.class)),
+				new File(pathOfJarContaining(KotlinPlatformJvmPlugin.class)),
+				new File(pathOfJarContaining(KotlinProject.class)),
+				new File(pathOfJarContaining(KotlinToolingVersion.class)),
 				new File(pathOfJarContaining("org.jetbrains.kotlin.daemon.client.KotlinCompilerClient")),
 				new File(pathOfJarContaining(KotlinCompilerPluginSupportPlugin.class)),
 				new File(pathOfJarContaining(LanguageSettings.class)),