imgcodecs: fix Apple conversions build without AVFoundation #29138Fixes#28553.
This PR fixes Apple imgcodecs conversion builds when AVFoundation is disabled or unavailable on older macOS SDKs.
Changes:
- Guard AVFoundation import with HAVE_AVFOUNDATION.
- Use older macOS-compatible framework imports when ImageIO is unavailable.
- Add __bridge compatibility for older Objective-C++ compilers.
- Use NSMakeSize for older macOS instead of passing CGSize to NSImage API.
Testing:
- Not tested locally: no macOS environment available.
- Patch follows the fix confirmed in #28555 discussion.
Expose CGImage <-> Mat conversion for iOS platforms
* Add apple_conversions to framework builds
This exposes CGImage <-> Mat conversion.
* Export Mat <-> CGImage methods on iOS targets
* Add CGImage converters to iOS objc helper class
* Add CF_RETURNS_RETAINED annotations to methods returning CGImageRef