cudacodec::VideoReader: force output frame resolution to be display not coded size

[cudawarped]

Now that cropping can automatically be applied inside cudacodec::VideoReader (#3355) in addition to the fixes in #3001 this PR automatically removes any redundant rows in decoded video's. E.g 1080p is internally decoded to 1920x1088, currently this results in a 1920x1088 frame being returned from VideoReader->nextFrame() which the user has to manually crop using the information contained in VideoReader::FormatInfo, with this PR it will result in a 1920x1080 frame being returned.

This resolves issues such as #3195 and opencv/opencv#21207 (comment)

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]

👍 Tested manually with CUDA 10.2, Ubuntu 18.04.