refactor: Modernize and optimize check_structure.py script

[geniruphin-junior]

Description

This Pull Request modernizes and optimizes the check_structure.py script by leveraging modern Python 3.10+ practices, improving memory consumption, and enforcing clean code standards.

Changes Made

• Architecture: Encapsulated the execution logic inside a proper main() function instead of running it raw under the __main__ block.
• Memory Optimization: Converted _find_misplaced_java_files to return an Iterator (generator expression) instead of building a full list in memory, which scales better as the repository grows.
• Clean Code & Readability:
  • Simplified the parent directory lookup by using java_file.parents directly.
  • Used any() for a cleaner and more idiomatic path validation logic.
  • Extracted hardcoded paths into a tuple constant (VALID_PATHS).
• CI/CD Best Practices: Redirected error outputs to sys.stderr instead of standard stdout, and added clear visual feedback (❌ / ✅) with file counters for better logs readability.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• The script runs without any bugs or regressions

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.24%. Comparing base (fd2858e) to head (03af606).
⚠️ Report is 24 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #7521 +/- ##
============================================
- Coverage 80.25% 80.24% -0.01% + Complexity 7358 7357 -1 
============================================
Files 810 810 Lines 23787 23787 Branches 4678 4678 ============================================
- Hits 19091 19089 -2 
Misses 3940 3940 - Partials 756 758 +2 

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[prashantpiyush1111]

Nice refactor overall. One suggestion: could you keep the inline comments and docstrings in English for consistency with the rest of the repository? The implementation looks good, but using a single language throughout the codebase makes maintenance easier.

[DenizAltunkapan]

i agree with @prashantpiyush1111