Updates for Swift 6

[johnfairh]

Code changes:

• SourceKit has broken SPI group extraction, have to fake it.
• SymGraph is generating duplicate conformances, have to uniq them.
• At some point Actor protocol changed to AnyActor
• SwiftPM moved the built module into a Modules directory…

Spec changes:

• Alamofire, RealmSwift - attribute ordering has been changed, in particular @autoclosure and @escaping have been reversed; more types are marked @MainActor.
• RealmObjC - many fewer symbols but these are all in “_private” header files eg. RLMAppSubscriptionToken, RLMUpdatePolicy. I think Clang must have improved to respect an #ifdef or something. Result is better.
• Moved jazzy test projects to require Swift 6

[johnfairh]

Couple of weird inconsistencies vs. local; some will be arm vs. intel - leave it like this for a few betas...