Make `WinSDK.GUID` conform to `CustomStringConvertible`.
This PR adds CustomStringConvertible conformance to GUID on Windows. This type is a currency type and being able to convert it to a string for display or debugging is very useful.
See also #84792.
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Could WinSDK.GUID also conform to LosslessStringConvertible, similar to the accepted proposal for Foundation's UUID? (The implementation at swiftlang/swift-foundation#1303 hasn't been merged yet.)
Could
WinSDK.GUIDalso conform toLosslessStringConvertible, similar to the accepted proposal for Foundation'sUUID? (The implementation at swiftlang/swift-foundation#1303 hasn't been merged yet.)
It could, sure. ~~I'd do it in a separate PR though.~~ I done did it.
@swift-ci test
@swift-ci smoke test Windows