Configure the Gradle toolchain to use Java 23

In order to be able to fix spring-projectsgh-34140 which requires using at least a
Java 22 compiler, this commit intends to change the configuration of the
Gradle toolchain to use Java 23, while setting the Java release to
Java 17 (or other versions when using MRJARs) when relevant in order to
keep the current Java 17 baseline.

See spring-projectsgh-34220

buildSrc/src/main/java/org/springframework/build/JavaConventions.java

@@ -73,7 +73,7 @@ public void apply(Project project) {
 	private void applyJavaCompileConventions(Project project) {
 		project.getExtensions().getByType(JavaPluginExtension.class).toolchain(toolchain -> {
 			toolchain.getVendor().set(JvmVendorSpec.BELLSOFT);
-			toolchain.getLanguageVersion().set(JavaLanguageVersion.of(17));
+			toolchain.getLanguageVersion().set(JavaLanguageVersion.of(23));
 		});
 		SpringFrameworkExtension frameworkExtension = project.getExtensions().getByType(SpringFrameworkExtension.class);
 		project.afterEvaluate(p -> {
@@ -83,6 +83,7 @@ private void applyJavaCompileConventions(Project project) {
 						compileTask.getOptions().setCompilerArgs(COMPILER_ARGS);
 						compileTask.getOptions().getCompilerArgumentProviders().add(frameworkExtension.asArgumentProvider());
 						compileTask.getOptions().setEncoding("UTF-8");
+						setJavaRelease(compileTask);
 					});
 			p.getTasks().withType(JavaCompile.class)
 					.matching(compileTask -> compileTask.getName().startsWith(JavaPlugin.COMPILE_TEST_JAVA_TASK_NAME)
@@ -91,9 +92,23 @@ private void applyJavaCompileConventions(Project project) {
 						compileTask.getOptions().setCompilerArgs(TEST_COMPILER_ARGS);
 						compileTask.getOptions().getCompilerArgumentProviders().add(frameworkExtension.asArgumentProvider());
 						compileTask.getOptions().setEncoding("UTF-8");
+						setJavaRelease(compileTask);
 					});
 
 		});
 	}
 
+	private void setJavaRelease(JavaCompile task) {
+		int defaultVersion = 17;
+		int releaseVersion = defaultVersion;
+		int compilerVersion = task.getJavaCompiler().get().getMetadata().getLanguageVersion().asInt();
+		for (int version = defaultVersion ; version <= compilerVersion ; version++) {
+			if (task.getName().contains("Java" + version)) {
+				releaseVersion = version;
+				break;
+			}
+		}
+		task.getOptions().getRelease().set(releaseVersion);
+	}
+
 }