Move back to the standard github workflow for modernisation platform

[MatMoore]

Background

We have diverged from the standard workflow by creating our own workflow: .github/workflows/reusable_terraform_plan_apply_test.yml

We did this as part of PoC for testing with terratest and smoke testing, but we probably shouldn't have let this become a permanent solution.

Task

Temporarily remove the smoke tests, and/or find a way to trigger them from the main workflow in a way that is reusable by other teams.

If we remove it temporarily, we can raise an issue with modernisation platform to add this functionality back in a way they can support.

Don't wait until we have finalised the testing work: we will likely improve tests bit by bit as our focus now is on the catalogue.

Stretch goal: David Eliot requested a demo for the MP of the tests working https://mojdt.slack.com/archives/C01A7QK5VM1/p1704463604108639?thread_ts=1704455070.725129&cid=C01A7QK5VM1

Value / Purpose

The current approach is creating friction for both us and modernisation platform team

• every time modernisation platform update something, it needs to be propagated to our workflow
• modernisation platform don't want to maintain an extra workflow that cannot be used by other teams
• it's not a good use of our time to keep track of what the modernisation platform is doing and change our workflow to keep it in sync with the main one

Example thread where this happened in January https://mojdt.slack.com/archives/C01A7QK5VM1/p1704455070725129

Response from Ewa Stempel https://mojdt.slack.com/archives/C01A7QK5VM1/p1704462864082089?thread_ts=1704455070.725129&cid=C01A7QK5VM1

this workflow is not part of the platform and we do not support it. If you need the features that your workflow provides and is not in our workflow, could you please raise an issue for it or propose a change that works for all? We will aim to retire your workflow, since it is not the service we provide (and must have skipped through the net when got approved I believe?)

Definition of Done

• We can retire the extra workflow
• We have a proposal for integrating with the main workflow OR the modernisation platform team understand what we need and we're happy to wait for it