Migrate app distro imports

Author: ncooke3

FirebaseAppDistributionInternal/Sources/ApiService.swift

@@ -17,8 +17,7 @@ import FirebaseInstallations
 import Foundation
 import UIKit
 
-// Avoids exposing internal APIs to Swift users
-@_implementationOnly import FirebaseCoreInternal
+internal import FirebaseCoreInternal
 
 enum Strings {
   static let errorDomain = "com.firebase.appdistribution.api"

FirebaseAppDistributionInternal/Sources/Internal/Logger.swift

@@ -15,7 +15,7 @@
 
 import Foundation
 
-@_implementationOnly import FirebaseCoreExtension
+internal import FirebaseCoreExtension
 
 ///
 /// Logger is responsible for printing console logs