Support Terraform 0.15 transition to internal go packaging

[sjourdan]

Description

Everything is in there: hashicorp/terraform#28723

The PR already includes examples of integrations.

[wbeuil]

Seems to me that it's going to impact several files on driftctl.

With a simple search for hashicorp/terraform on our repo, we use /plugin /terraform and /providers who are now under /internal.

[sjourdan]

Action: investigate which areas of Terraform driftctl depends on. Check other community project solutions.
Evaluate real impact.

with 1.0.0 released: the state format won't change anytime soon for 18 months +.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.