fix(Auth): Adding credentialsProvider to Cognito clients (#3745)

* fix(Auth): Adding credentialsProvider to Cognito clients

* revert making the credentials provider initializer public

Author: harsh62

AmplifyPlugins/Auth/Sources/AWSCognitoAuthPlugin/AWSCognitoAuthPlugin+Configure.swift

@@ -7,7 +7,6 @@
 
 import Foundation
 @_spi(InternalAmplifyConfiguration) import Amplify
-
 import AWSCognitoIdentity
 import AWSCognitoIdentityProvider
 import AWSPluginsCore
@@ -112,6 +111,9 @@ extension AWSCognitoAuthPlugin {
                 configuration.retryStrategyOptions = RetryStrategyOptions(maxRetriesBase: Int(maxRetryUnwrapped))
             }
 
+            let authService = AWSAuthService()
+            configuration.credentialsProvider = authService.getCredentialsProvider()
+
             return CognitoIdentityProviderClient(config: configuration)
         default:
             fatalError()
@@ -134,6 +136,9 @@ extension AWSCognitoAuthPlugin {
                 configuration.retryStrategyOptions = RetryStrategyOptions(maxRetriesBase: Int(maxRetryUnwrapped))
             }
 
+            let authService = AWSAuthService()
+            configuration.credentialsProvider = authService.getCredentialsProvider()
+
             return CognitoIdentityClient(config: configuration)
         default:
             fatalError()