ci(tofu-apply): Allow passing args to `tofu apply`

Add a new TF_PLAN_APPLY_ARGS variable that can be used to tweak how tofu apply does it's work. We are also now always passing -auto-approve to tofu apply so that OpenTofu will actually try to do some work. The default tofu apply behavior is to abort when it realises that it is being run non-interactively.

Bug: T372498