Import FoundationNetworking in test files

Conditionally import FoundationNetworking in tests to support platforms (e.g. Linux) where networking APIs live outside Foundation. Added `#if canImport(FoundationNetworking) import FoundationNetworking #endif` to APIClientTests.swift, MockURLHandlerStore.swift, and MockURLProtocol.swift.

Author: artemkalinovsky

Tests/KiteTests/APIClientTests/APIClientTests.swift

@@ -6,6 +6,9 @@
 //
 
 import Foundation
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
 import Kite
 import Testing
 

Tests/KiteTests/Mocks/MockURLHandlerStore.swift

@@ -6,6 +6,9 @@
 //
 
 import Foundation
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
 
 final actor MockURLHandlerStore {
     private typealias Handler = @Sendable (URLRequest) throws -> (Data, URLResponse)

Tests/KiteTests/Mocks/MockURLProtocol.swift

@@ -6,6 +6,9 @@
 //
 
 import Foundation
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
 
 final class MockURLProtocol: URLProtocol, @unchecked Sendable {
     enum Error: Swift.Error {