Code refactoring and more operators support

Refactor some code to comply with OpenCV's coding style and make the
logic clearer.

Rename some class names:
| Object    | CANN                     | CUDA     |
| --------- | ------------------------ | -------- |
| Namespace | cv::cann                 | cv::cuda |
| Matrix    | AclMat -> NpuMat         | GpuMat   |
| Stream    | AclStream -> AscendStrem | Stream   |
| Event     | AclEvent  -> AscendEvent | Event    |

Add more operators:
- [x] bitwise_not
- [x] addWeighted
- [x] crop
- [x] cvtColor (support part of color formats)
- [x] merge
- [x] split
- [x] rotate
- [x] flip
- [x] threshold
- [x] transpose

Co-authored-by: CaoMengqing <cmq0113@163.com>

Author: hipudding