Fix CodeTailor Java support and Parsons block granularity

[aspadiyath]

• Fix backup/static Parsons puzzle including the question's instruction text as a draggable block — extract_parsons_code now extracts only the code inside <pre class="parsonsblocks">, excluding the sibling <div class="parsons_question"> prompt text.
• Fix Java CodeTailor personalization always failing and falling back to the generic error:
  • The JOBE test runner called {test_class}.main(args) on JUnit test classes (extending CodeTestHelper, @Test-annotated) that have no main(), so every Java run failed to compile. Now runs tests via JUnitCore.runClasses(...), matching the convention already used by the regular (non-CodeTailor) Java activecode runner.
  • The student's class was only referenced by name reflectively (super("ClassName")), so javac never compiled it, causing a runtime ClassNotFoundException. Now explicitly passed via compileargs.
  • Removed a dead helper (inject_pass_fail_prints) that assumed the old, incorrect main()-based test convention.
• Fix Parsons blocks grouping multiple statements at the same indentation level into a single draggable block instead of one block per statement, in both the "Full" puzzle path (split_java_code_into_blocks) and the "Partial"/distractor puzzle path (aggregate_code_to_Parsons_block_with_distractor).