Invocations of a method-ordered class template should run in parallel by default

[t-o-n-y-p]

Following the discussion here #5023

Steps to reproduce

1. Set up parallel test execution, for example, with 4 fixed threads
2. Write a method-ordered test class annotated with @TestMethodOrder(MethodOrderer.OrderAnnotation.class) and with order being assigned to its test methods
3. Declare this class a template and make a couple of invocations for it
4. Run the test class. Code example is provided below

junit.jupiter.execution.parallel.enabled=true
junit.jupiter.execution.parallel.mode.default=concurrent
junit.jupiter.execution.parallel.config.strategy=fixed
junit.jupiter.execution.parallel.config.fixed.parallelism=4

@ExtendWith(MethodOrderedClassTemplateExtension.class)
@ClassTemplate
@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
public class MethodOrderedClassTemplateTest {

  @Test
  @Order(0)
  void test1() throws InterruptedException {
    Thread.sleep(2000);
  }

  @Test
  @Order(1)
  void test2() throws InterruptedException {
    Thread.sleep(2000);
  }
}

@NullMarked
public class MethodOrderedClassTemplateExtension implements ClassTemplateInvocationContextProvider {
  @Override
  public boolean supportsClassTemplate(ExtensionContext context) {
    return true;
  }

  @Override
  public Stream<? extends ClassTemplateInvocationContext> provideClassTemplateInvocationContexts(ExtensionContext context) {
    return Stream.of(new ClassTemplateInvocationContext() {}, new ClassTemplateInvocationContext() {});
  }
}

Expected result

Invocations are being run in parallel while test method order is being respected within each invocation

Actual result

Invocations are being run sequentially

Context

• Used versions (Jupiter/Vintage/Platform): 6.0.0
• Build Tool/IDE: IntelliJ IDEA 2025.2.2