sample(storage): Soft deleted Bucket Restore

[shubhangi-google]

Add support for restoring soft deleted bucket.

Operation Supported:

• Get Bucket Generation
• Get a Soft Deleted Bucket (Also soft-delete time and hard-delete time)
• List Soft Deleted Buckets
• Restore a Soft Deleted Bucket

@example
require "google/cloud/storage"
storage = Google::Cloud::Storage.new
bucket = storage.bucket "my-bucket"
bucket.delete
##fetch bucket generation
 generation= bucket.generation
## list soft_deleted buckets
deleted_buckets= storage.buckets soft_deleted: true
## restore bucket
bucket = storage.restore_bucket "my-bucket", generation