feat: add cr_checker

[MaximilianSoerenPollak]

Moving cr_checker from the tooling repository.
To start the splitting up process of the tooling repo.

This still has a dependency to tooling as python_basics has not been moved yet.
This will be independed once that is done too.

[MaximilianSoerenPollak]

Does it need the exclusion as well?

[MaximilianSoerenPollak]

Remove? As the parent dir has one already?

[MaximilianSoerenPollak]

See if this can be upgraded?

[AlexanderLanin]

Re-review

Re-reviewed after fix: remove not needed LICENCE (6e4236e) and fix: fix Pr comments (caf036c).

✅ Both remaining bugs fixed

• load_exclusion — now builds a fresh list (appends only valid entries) instead of aliasing and mutating during iteration. The skip-after-removal bug is gone.
• Macro data — the template/exclusion appends moved outside the for t_name loop, so data is built once. The .fix target no longer gets duplicate labels; bazel run //:copyright-fix is no longer at risk.

✅ Minor items also addressed

• import json removed from tests/test_cr_checker.py.
• templates.ini kept in py_library.srcs but now documented with the rationale (avoids runtime path resolution) — reasonable call.
• Bumped aspect_rules_py 1.4.0 → 1.6.3; dropped the stray cr_checker/LICENSE.

Verified locally: pytest cr_checker/tests/ → 68 passed.

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Verdict: All findings from prior reviews are resolved. Nothing blocking remains from my side. 👍

(Only nit left, non-blocking: path = Path(item) in load_exclusion still shadows the path parameter — cosmetic, since path isn't used after the loop.)