Use app…DefaultJvmArgs as convention for start script's defaultJvmOpts

Closes gh-12631

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

@@ -73,6 +73,14 @@ public class ApplicationPluginActionIntegrationTests {
 						.contains("bootStartScripts exists = true");
 	}
 
+	@Test
+	public void createsBootStartScriptsTaskUsesApplicationPluginsDefaultJvmOpts() {
+		assertThat(this.gradleBuild
+				.build("startScriptsDefaultJvmOpts", "-PapplyApplicationPlugin")
+				.getOutput()).contains(
+						"bootStartScripts defaultJvmOpts = [-Dcom.example.a=alpha, -Dcom.example.b=bravo]");
+	}
+
 	@Test
 	public void zipDistributionForJarCanBeBuilt() throws IOException {
 		assertThat(