ModuleDiscoverer unit tests

[ascopes]

We need to write a couple of unit tests for the module discoverer utility class.

https://github.com/ascopes/java-compiler-testing/blob/main/java-compiler-testing/src/main/java/io/github/ascopes/jct/utils/ModuleDiscoverer.java

These tests should be fine to just static-mock the internal module finder class.

In addition, since it is a utility class, the test class should implement the UtilityClassTestTemplate at https://github.com/ascopes/java-compiler-testing/blob/main/java-compiler-testing/src/test/java/io/github/ascopes/jct/tests/helpers/UtilityClassTestTemplate.java

For example:

@DisplayName("ModuleDiscoverer tests")
@ExtendWith(MockitoExtension.class)
class ModuleDiscovererTest
    implements UtilityClassTestTemplate {

  @Mock
  MockStatic<ModuleFinder> moduleFinderClass;

  @Mock
  ModuleFinder moduleFinderInstance;

  @BeforeEach
  void setUp() {
    moduleFinder
        .when(() -> ModuleFinder.of(any()))
        .thenReturn(moduleFinderInstance);
  }

  ...
}