@MainActor in bridged code uses MainActor.assumeIsolated which is only available in iOS 17

[marcprux]

The CI failure on macOS 13 raises the issue of:

@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
nonisolated public func assumeIsolated<T>(_ operation: (isolated Self) throws -> T, file: StaticString = #fileID, line: UInt = #line) rethrows -> T where T : Sendable

resulting in this test failure:

/Users/runner/work/skip-bridge/skip-bridge/.build/plugins/outputs/skip-bridge/SkipBridgeToKotlinSamplesTests/skipstone/SkipBridgeToKotlinSamples/.build/SkipBridgeToKotlinSamples/swift/plugins/outputs/swift/SkipBridgeToKotlinSamples/skipstone/SkipBridgeGenerated/Samples_Bridge.swift:854:22: error: 'assumeIsolated(_:file:line:)' is only available in macOS 14.0 or newer
    return MainActor.assumeIsolated {

There may be no solution other than documenting that @ MainActor is limited to iOS 17+.