fix: Use property accessors on Frame (#2400)

* fix: Use property accessors on `Frame`

* Format

* Use `_Nonnull`

* fix: Assume nonnull

* Use `NS_ASSUME_NONNULL_BEGIN` more

* Format C++

package/ios/Frame Processor/FrameProcessor.h

@@ -19,6 +19,8 @@
 #import <memory.h>
 #endif
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface FrameProcessor : NSObject
 
 - (instancetype)init NS_UNAVAILABLE;
@@ -30,6 +32,8 @@
 - (void)callWithFrameHostObject:(std::shared_ptr<FrameHostObject>)frameHostObject;
 #endif
 
-- (void)call:(Frame* _Nonnull)frame;
+- (void)call:(Frame*)frame;
 
 @end
+
+NS_ASSUME_NONNULL_END