Descripe the feature and motivation

Some 3d related algorithms use NAN for points in cloud/depth/volume to mark invalid values. Function that generates mask with NANs, but not patch it will be useful.

Usage examples:

• https://github.com/opencv/opencv/blob/5.x/modules/3d/test/test_normal.cpp#L378
• https://github.com/opencv/opencv/blob/5.x/modules/3d/test/test_tsdf.cpp#L758

Related issue: #16465
Stack Overflow discussion: https://stackoverflow.com/questions/41759247/filter-opencv-mat-for-nan-values

Proposed signature:

CV_EXPORTS_W void nanMask(InputArray img, OutputArray mask);

SSE/AVX/NEON optimizations may be reused from existing patchNans code.

Additional context

No response