Concurrency safe handler

[sidepelican]

Issue: #249

When the mock protocol requires Sendable, correctly implement the mock functions as Sendable. To provide a concurrency-safe implementation, we also add some helper functions and types.

This PR does not address stored properties or computed properties (Do it later).

As shown below, various function Handlers are required to be Sendable.

/// @mockable
protocol APIClient: Sendable {
    func fetchData(_ id: AnyObject) async -> Int
}

final class APIClientMock: APIClient {
    init() { }

    private let fetchDataState = MockoloMutex(MockoloHandlerState<AnyObject, @Sendable (AnyObject) async -> Int>())
    var fetchDataCallCount: Int {
        return fetchDataState.withLock(\.callCount)
    }
    var fetchDataArgValues: [AnyObject] {
        return fetchDataState.withLock(\.argValues).map(\.value)
    }
    var fetchDataHandler: (@Sendable (AnyObject) async -> (Int))? {
        get { fetchDataState.withLock(\.handler) }
        set { fetchDataState.withLock { $0.handler = newValue } }
    }
    func fetchData(_ id: AnyObject) async -> Int {
        warnIfNotSendable(id)
        let handler = fetchDataState.withLock { state in
            state.callCount += 1
            state.argValues.append(.init(id))
            return state.handler
        }
        if let handler {
            return await handler(id)
        }
        return 0
    }
}

[sidepelican]

I changed the implementation because the processing became more complex.

[sidepelican]

Instead of examining all lines, we check whether the output lines contain the fixture.