Add LoadCmix functor

Sources/ElixxirDAppsSDK/LoadCmix.swift

+import Bindings
+import XCTestDynamicOverlay
+
+public struct LoadCmix {
+  public var run: (String, Data, Data) throws -> Cmix
+
+  public func callAsFunction(
+    storageDir: String,
+    password: Data,
+    cmixParamsJSON: Data
+  ) throws -> Cmix {
+    try run(storageDir, password, cmixParamsJSON)
+  }
+}
+
+extension LoadCmix {
+  public static let live = LoadCmix { storageDir, password, cmixParamsJSON in
+    var error: NSError?
+    let bindingsCmix = BindingsLoadCmix(storageDir, password, cmixParamsJSON, &error)
+    if let error = error {
+      throw error
+    }
+    guard let bindingsCmix = bindingsCmix else {
+      fatalError("BindingsLoadCmix returned `nil` without providing error")
+    }
+    return Cmix.live(bindingsCmix)
+  }
+}
+
+extension LoadCmix {
+  public static let unimplemented = LoadCmix(
+    run: XCTUnimplemented("\(Self.self)")
+  )
+}