drt: check spacing from concave corners

[naveenvenk17]

Concave LEF58 corner-spacing checks never reached the distance test. The code required the corner to be an exact corner of a maximal rectangle, but a concave point sits on the boundary of the two rectangles that form the notch.

Match concave corners against those boundary edges based on their orientation. Convex corner handling stays unchanged. The old disabled regression is enabled and expanded to cover all four notch orientations.

Testing on the GCP VM:

• bazel test //src/drt/test:gc_unittest //src/drt/test:ta_unittest
• bazel build --config=lint //src/drt //src/drt/test:gc_unittest
• bazel test --config=asan //src/drt/test:gc_unittest --test_env=ASAN_OPTIONS=detect_leaks=0 with the ASan setup from bazel: fix hermetic ASan builds #10911 layered locally

The ASan run covered all 105 geometry-check tests.

[gemini-code-assist]

Code Review

This pull request implements concave corner overlap detection in FlexGCWorker::Impl::isCornerOverlap and introduces a parameterized test suite to verify concave corner spacing violations across all orientations. The reviewer suggests extending this concave corner handling to the second overload of isCornerOverlap to ensure consistency and prevent potential bugs.