add gcs module, this fixes the initialization chainstorage

[HenryYYang]

What changed? Why?

This fixes the following error whenever we try to start chainstorage. failed to build internal.BlobStorage:\nmissing dependencies for function \"[github.com/coinbase/chainstorage/internal/storage/blobstorage/internal\](http://github.com/coinbase/chainstorage/internal/storage/blobstorage/internal%5C)".WithBlobStorageFactory\n\t/app/internal/storage/blobstorage/internal/blobstorage.go:32:\nmissing type:\n\t- internal.BlobStorageFactory[name=\"blobstorage/gcs\"] (did you mean to Provide it?)

How did you test the change?

• [ ] unit test
• [ ] integration test
• [ ] functional test
• [ ] adhoc test (described below)