[Feature request] Add cv2.INTER_NEAREST_EXACT, cv2.INTER_LINEAR_EXACT interpolation to cv2.warpAffine

[ternaus]

Describe the feature and motivation

Currently cv2.warpAffine does not support cv2.INTER_NEAREST_EXACT, cv2.INTER_LINEAR_EXACT interpolation modes. But for problems of image segmentations, where pixel level accuracy is important for prediction values on the border would be great to have them.