Fix swiftlint warnings in the facebook-ios-sdk (#1559)

Summary:
Pull Request resolved: https://github.com/facebook/facebook-ios-sdk/pull/1559

This commit fixes the current swiftlint warnings in the SDK.

- Added a blank line between "import Foundation" and "testable import FBSDKCoreKit" to fix sorted_imports.
- Excluded "RawAppEventsConfigurationResponseFixtures" in .swiftlint.yml for the type_name violation.
- Ignored the trailing_comma rule to allow trailing commas.

The following warnings were fixed:
```
warning: Colon Violation: Colons should be next to the identifier when specifying a type and next to the key in dictionary literals. (colon)
warning: Type Name Violation: Type name should be between 3 and 40 characters long: 'RawAppEventsConfigurationResponseFixtures' (type_name)
warning: Sorted Imports Violation: Imports should be sorted. (sorted_imports)
warning: Vertical Whitespace Violation: Limit vertical whitespace to a single empty line. Currently 2. (vertical_whitespace)
```

Reviewed By: joesus

Differential Revision: D24691969

fbshipit-source-id: 4fc7a87d613d7053eccbd49519e93206a32b97ef

testing/TestXcodeIntegration/TestXcodeIntegration/AppDelegate.swift

@@ -19,15 +19,13 @@
 import UIKit
 
 import FBSDKCoreKit
+import FBSDKGamingServicesKit
 import FBSDKLoginKit
 import FBSDKShareKit
-import FBSDKGamingServicesKit
 
 @UIApplicationMain
 class AppDelegate: UIResponder, UIApplicationDelegate {
 
-
-
     func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
         // Override point for customization after application launch.
         return true
@@ -46,6 +44,4 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
         // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
         // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
     }
-
-
 }

testing/TestXcodeIntegration/TestXcodeIntegration/SceneDelegate.swift

@@ -22,7 +22,6 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate {
 
     var window: UIWindow?
 
-
     func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
         // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
         // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
@@ -57,6 +56,4 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate {
         // Use this method to save data, release shared resources, and store enough scene-specific state information
         // to restore the scene back to its current state.
     }
-
-
 }