Make 64 bit int a 64 bit int in Swift

[juliettebee]

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Hi! I'm working on a Jellyfin client, one of the platforms I'm supporting is the Apple Watch. The Apple Watch is only 64 bit when specified and as a result when integers are above the 32 bit limit there's an error. This PR fixes that issue. However, it requires slight change of code for clients as it's changing the data type. Thank you so much, have a good night!

[LePips]

This is not a negligible change and something I'll have to think about. I will probably initially have this in a separate branch for "32 bit support" until I think about a Swiftfin Apple Watch app.

Too bad the server stores these runtimes as microseconds.