`make_tf` currently uses DVC-machine specific directory/namespacing behavior

[pmrowla]

We create separate terraform workspaces per named iterative-machine instance here.

tpi/tpi/terraform.py

Line 26 in c7259a8

def make_tf(self, name: str):

TPI should probably be more generic and just run everything within a single workspace based on whatever gets passed into TerraformBackend.__init__() (and the code for handling separate per-machine workspaces should be moved back into dvc.machine)