Add bigvision copyright #25520
This pull request adds Bigvision LLC to the copyright list to recognize our contributions to the project [#25433, #25415, #25304]. This update reflects our ongoing commitment to supporting and maintaining this project. Please let me know if there are any adjustments you would like me to make. Thank you for considering this addition.
changed OpenCV license from BSD to Apache 2 license
* as discussed and announced earlier, changed OpenCV license from BSD to Apache 2. Many files still contain old-style copyrights though
* changed wording a bit; preserve the original OpenCV BSD license