Replace legacy image downloader with new actor-based implementation

Sources/MapboxNavigation/ImageDownloader/ImageDownloader.swift

@@ -0,0 +1,5 @@
+import Foundation
+
+protocol ImageDownloaderProtocol {
+    func download(with url: URL, completion: @escaping (Result<CachedURLResponse, Error>) -> Void)
+}

Sources/MapboxNavigation/ImageDownloader/LegacyImageDownloader.swift

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+import Foundation
+
+@available(iOS, deprecated: 13.0, message: "Use ImageDownloader instead.")
+final class LegacyImageDownloader: ImageDownloaderProtocol {
+    private let urlSession: URLSession
+
+    init(configuration: URLSessionConfiguration? = nil) {
+        let defaultConfiguration = URLSessionConfiguration.default
+        defaultConfiguration.urlCache = URLCache(memoryCapacity: 5 * 1024 * 1024, diskCapacity: 20 * 1024 * 1024, diskPath: nil)
+        self.urlSession = URLSession(configuration: configuration ?? defaultConfiguration)
+    }
+
+    func download(with url: URL, completion: @escaping (Result<CachedURLResponse, Error>) -> Void) {
+        urlSession.dataTask(with: URLRequest(url)) { data, response, error in
+            if let response, let data {
+                completion(.success(CachedURLResponse(response: response, data: data)))
+            } else if let error {
+                completion(.failure(error))
+            }
+        }.resume()
+    }
+}

Sources/MapboxNavigation/ImageDownloader/ModernImageDownloader.swift

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+import Foundation
+
+enum DownloadError: Error {
+    case serverError
+    case clientError
+    case noImageData
+}
+
+@available(iOS 13.0, *)
+actor ImageDownloader: ImageDownloaderProtocol {
+    private let urlSession: URLSession
+
+    private var inflightRequests: [URL: Task<CachedURLResponse, Error>] = [:]
+
+    init(configuration: URLSessionConfiguration? = nil) {
+        let defaultConfiguration = URLSessionConfiguration.default
+        defaultConfiguration.urlCache = URLCache(memoryCapacity: 5 * 1024 * 1024, diskCapacity: 20 * 1024 * 1024)
+        self.urlSession = URLSession(configuration: configuration ?? defaultConfiguration)
+    }
+
+    nonisolated func download(with url: URL, completion: @escaping (Result<CachedURLResponse, Error>) -> Void) {
+        Task {
+            do {
+                let response = try await self.fetch(url)
+                completion(.success(response))
+            } catch {
+                completion(.failure(error))
+            }
+        }
+    }
+
+    private func fetch(_ url: URL) async throws -> CachedURLResponse {
+        if let inflightTask = inflightRequests[url] {
+            return try await inflightTask.value
+        }
+
+        let downloadTask = Task<CachedURLResponse, Error> {
+            let (data, response) = try await urlSession.data(from: url)
+            return CachedURLResponse(response: response, data: data)
+        }
+        inflightRequests[url] = downloadTask
+        let response = try await downloadTask.value
+        inflightRequests[url] = nil
+
+        return response
+    }
+}