ccalib: add k3 radial distortion support for omnidir model

[nechami795]

Summary

Add k3 support to the omnidirectional distortion model in ccalib.

Related issue
Fixes #3952

Details

• Support both 4- and 5-parameter distortion vectors in omnidir APIs.
• Preserve backward compatibility when k3 = 0.
• Update the relevant mono and stereo omnidir code paths to support k3.

Tests

• Added real-data and synthetic tests for mono and stereo omnidir calibration.
• Added backward-compatibility tests verifying equivalence between the legacy 4-parameter model and the 5-parameter model with k3 = 0.
• Added real-data sanity tests for the 5-parameter model and golden-regression tests for the legacy 4-parameter model.
• Added synthetic tests showing that enabling free k3 improves reprojection fit and recovers non-zero k3 when present in the ground truth.
• Added validation for undistortion, rectification, and map generation, including k3 = 0 equivalence checks.

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
• The PR is proposed to the proper branch
• There is a reference to the original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake

[asmorkalov]

The tests you added are very soft and check mostly nothing. Please enhance the tests with real coordinates / distortion coefficients check.

[nechami795]

The tests you added are very soft and check mostly nothing. Please enhance the tests with real coordinates / distortion coefficients check.

Thank you for the comment.
I've run full process with real coordinates, but I did that from a separate standalone .cpp, not from tests.
Right now I am improving the code, will make additional test later.