Improved the way mapping results are shown

[dylanratcliffe]

Fixes: overmindtech/aws-source#518

This makes the resource mapping output much clearer, we now show why something wasn't mapped if it is supported, rather than showing it as unsupported:

✔︎ Extracting 2 changing resources: 1 supported 1 unsupported
  ✔︎ aws_instance (1)
  ✗ aws_iam_role (1)

To:

✔︎ Extracting 4 changing resources
  ✔︎ module.scenarios[0].aws_iam_role.test_role (mapped)
  ? module.scenarios[0].aws_iam_role.test_role (missing arn)
  ✗ module.scenarios[0].aws_iam_role.test_role (not supported)