Support Swift 5.10 and Swift 6

• Support nonisolated(unsafe).
  https://github.com/apple/swift-evolution/blob/main/proposals/0412-strict-concurrency-for-global-variables.md
• Support typed throws.
  https://github.com/swiftlang/swift-evolution/blob/main/proposals/0413-typed-throws.md
• Support sending keyword.
  https://github.com/swiftlang/swift-evolution/blob/main/proposals/0430-transferring-parameters-and-results.md
• Other fixes and CI improvements.