Turning `task` into an importable module

[0x2b3bfa0]

Terraform providers modules are named in such a way that prevents importing them. Now that we're going to use the task package from several repositories, we'll need to perform some modifications so it can be imported.

Option A

Rename terraform-provider-iterative to github.com/iterative/terraform-provider-iterative here and on every imaginable import:

terraform-provider-iterative/go.mod

Line 1 in 85645f4

module terraform-provider-iterative

Option B

Create a new github.com/iterative/leo repository/module and move the task package (also cmd) and children there.

[0x2b3bfa0]

(I prefer option B)

[tasdomas]

To be clear - the way terraform provider modules are named has no technical reason behind it. It's just a means of not having to maintain a stable API. Nothing will break if we change the module name of terraform-provider-iterative.