Be able to use all states within a directory

[eliecharra]

Description
We want to allow to read a whole directory as IaC input.

Example

$ driftctl scan --tfstate://my-states/*.tfstate

[sjourdan]

LGTM!

I tested with multiple states + an out of sync s3 state:

Found unmanaged resources:
  aws_s3_bucket:
    - s3-bucket-1-6qaidu

then I sync'd the state locally:

Found 1 resource(s)
 - 100% coverage
Congrats! Your infrastructure is fully in sync.