gcp client code migration from aws-sdk v2 to v3

With the migration we can no longer use the serviceDefine
property available with aws-sdk v2. This commit aims to extend
the s3Client class to override the methods that are not
compatible with GCP.

Issue: ARSN-514

Author: benzekrimaha

index.ts

@@ -153,9 +153,8 @@ export const storage = {
             AwsClient: require('./lib/storage/data/external/AwsClient'),
             AzureClient: require('./lib/storage/data/external/AzureClient'),
             GcpClient: require('./lib/storage/data/external/GcpClient'),
-            GCP: require('./lib/storage/data/external/GCP/GcpService'),
+            GCP: require('./lib/storage/data/external/GCP'),
             GcpUtils: require('./lib/storage/data/external/GCP/GcpUtils'),
-            GcpSigner: require('./lib/storage/data/external/GCP/GcpSigner'),
             PfsClient: require('./lib/storage/data/external/PfsClient'),
             backendUtils: require('./lib/storage/data/external/utils'),
         },