Migrate won't resolve a generated TableName

When providing raw CloudFormation code in the `resources` section of `serverless.yml`, you are able to leave out the `TableName` and have it default to the arn that serverless will assign it [based on the format outlined here](https://serverless.com/framework/docs/providers/aws/guide/resources#aws-cloudformation-resource-reference).

This is a great approach to defining table names so that your multiple stages will have their own tables, etc. Though, when trying to run `sls dynamodb migrate` it tells me that a missing `TableName` param is required.

Is this an error? Or is this a feature that needs to be added?

Start by reproducing `sls dynamodb migrate` with raw CloudFormation resources that omit `TableName`, then inspect how migration resolves table definitions. Done means generated table names are resolved consistently with Serverless and migration no longer reports a missing `TableName` parameter.

Written by the indexing model from the issue text.