Support TestNG class level annotations

Consider adding support for TestNG class level annotations.

https://testng.org/doc/documentation-main.html#class-level

With TestNG the @Test annotation can be placed on a class instead of the method. In this case all public void methods are considered tests even if they are not annotated.

Example:

@Test
public class TestNGTest {

  public void test1() {
    System.out.println("Test 1");
  }

  public void test2() {
      System.out.println("Test 2");
  }

  private void privateMethod() {
    System.out.println( "Not a test" );
  }
}

Currently there does not appear to be any way to run a test unless it is explicitly annotated. Right clicking and selecting Run just pops up an alert with No tests in file: .... No code lens appear at either class or method level. No tests appear under the class in the Test panel.

Start with the TestNG class-level annotation documentation linked in the issue and reproduce the reported "No tests in file" behavior using the Java example. Locate the existing TestNG test-discovery entry point and add coverage for public methods inherited from a class-level @Test while excluding private methods. Done means the tests run and appear in code lenses and the Test panel.