Unify Xcode projects

This unifies the Xcode projects for iOS, macOS and tvOS. It also cleans various avoidable duplication between the platforms.

changed milestone to %4.0

added 10 commits

• 97319629...6f9488b8 - 2 commits from branch videolan:master
• ed242523 - Add VLCKit for macOS to the MobileVLCKit xcodeproj
• 0cee56f3 - Remove previous VLCKit xcodeproj (macOS only) and rename MobileVLCKit xcodeproj for unifycation
• c2a275a6 - Move libvlc plugin headers to the correct place
• 0f0ed21a - Remove unused legacy script
• 66aafcc8 - Use a singular prefix header for all targets
• 793888c9 - Use a singular Info.plist for all platforms
• 2bad6069 - Unify helper code
• d1649a23 - Slightly reorder the xcodeproj

Compare with previous version

merged