Support `--create-fsx` flag within `aws-batch forge` command

[abhi18av]

As of now, when compared to the EFS options, it is not completely intuitive that it is possible to create an FSX filesystem from the tw CLI, even if it is possible to actually use --fsx-size to achieve the same result.

I suggest that we add a "proxy" --create-fsx command to have a more consistent behavior.

• EFS options

      --create-efs
      --efs-id
      --efs-mount

• FSx options

      --fsx-size
      --fsx-dns
      --fsx-mount