Add AddMissingTestAnnotation recipe to flag (or add) missing @Test annotations

[Vinu2111]

• Fixes Recipe to add missing @Test annotations #772

What's changed?

Adds AddMissingTestAnnotation, which finds forgotten tests: methods in an existing test class that are void, non-private, non-static, take no parameters, have a name starting with test, and contain at least one assertion (JUnit 4/5, AssertJ, Hamcrest, Mockito verify).

• Default: flag only. Matching methods get a search-result marker and nothing is modified.
• Opt-in addAnnotation=true adds @Test, matching the framework the class already uses (JUnit 4 or 5).
• Classes with both JUnit 4 and 5 @Test methods, or with no @Test method, are left untouched.
• Methods that already carry a test or lifecycle annotation are skipped.

What's your motivation?

Tests that lose their @Test annotation silently stop running. Following the discussion in #772, @timtebeek was hesitant about annotating automatically (for example a deliberately disabled database test), so the default only flags.

Anything in particular you'd like reviewers to focus on?

• The heuristic requires both a test name prefix and an assertion. This avoids turning helpers like testDataSetup() into tests, but misses real tests without the prefix, or ones asserting through custom helpers.
• Leaving classes that mix JUnit 4 and 5 untouched.

Have you considered any alternatives or workarounds?

"Name OR assertion" catches more tests, but it would annotate helpers, which RemoveTestPrefix could then rename.

Any additional context

• 24 tests in AddMissingTestAnnotationTest: positive and negative cases, JUnit 4 and 5, mixed classes, AssertJ/Hamcrest/Mockito, lifecycle annotations, the default (null) option, abstract methods and nested classes.
• recipes.csv contains only the new entry. I ran the test class and recipeCsvGenerate locally, but not a full ./gradlew build, so I'm relying on CI for that. My local dependency setup changed other rows' counts when regenerating, so I did not commit those.
• Known limitation: a package-private helper named test... that asserts would still be annotated in opt-in mode.
• Questions: is cleanup the right package, and should the recipe be added to a composite recipe (for example in cleanup.yml)? I left that out for now.

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've run ./gradlew build locally, and committed any resulting changes to recipes.csv
• I've formatted the lines I changed, without reformatting code I didn't touch