Support consuming and generating XCFramework with CMake

According to Apple documentation, XCFramework is a "is a distributable binary package created by Xcode that contains variants of a framework or library so that it can be used on multiple platforms (iOS, macOS, tvOS, and watchOS), including Simulator builds. An XCFramework can be either static or dynamic and can include headers."

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XCFramework was introduced with XCode 11 in 2019. Now, with the introduction of Apple Silicon, XCFramework is getting more interesting, since it can also encompass different CPU architectures even for the same platform".

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The main users for this would be those who provide an own SDK on top of Qt which should support multiple targets and architectures. 

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Apparently, the best-known way to use it is the XCode only. It looks like there are some tricks possible on the command line too https://developer.apple.com/forums/thread/126880

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PS. Yes, I found QTBUG-86387 before posting this one, but I dicided to not change it and create a new one instead which will not be focused on qmake