Add commands to support managing GitLab-managed OpenTofu / Terraform states

The goal is to add commands to support managing GitLab-managed OpenTofu / Terraform states.

Implementation Plan

Command to locally initialize the state: glab opentofu init <state-name>
Command to list states: glab opentofu state list
Command to download states: glab opentofu state download <state-name> [<serial>]
Commands to lock and unlock states: glab opentofu state (lock|unlock) <state-name>
Command to delete states: glab opentofu state delete <state-name> [<serial>]

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information