[Feature] Refactor dev setup to accomodate for opentofu

[scott-the-programmer]

Currently, bits of the validation setup (see the Makefile and the contributing guide) assume that the developer is using terraform. With the emergence of opentofu, this is not strictly the case anymore. We amend the setup / guide to accommodate this

The success criteria is that I should be able to run the equivalent of make test-stack without terraform installed