Extended DNN testing in GHA
* Extended DNN testing in GHA for 3.4 branch
* Updated docker images in Linux GitHub Actions
* Added OPENCV_DOWNLOAD_PATH flag for ARM build to use pre-downloaded binaries
Added workflow for Github Actions to build and test OpenCV on Windows for 3.4 branch
* Added workflow for Github Actions to build and test OpenCV on Windows
* Updated Github Actions for 3.4 branch on Windows using self-hosted runner
* Fixed url for a fork in Windows workflow (3.4 branch)
* opencv_extra fork usage in Github Actions
Added workflow for Github Actions to build and test OpenCV on Linux
* Added workflow for Github Actions to build and test OpenCV
* Merged a build and tests in one job, changed naming
* Renamed job names, split workflows by branch, removed and added some cmake flags, save unit tests results as a html file
* Split tests by steps, removed workflows for 4.x and 5.x branches