Consider setting up this repository to test if upgrade workflows succeed

[guineveresaenger]

It would be great if upgrade-provider Workflows such as this one could be tested in this repository.

[danielrbradley]

I've made some progress towards this:

1. Created 2 releases of the upstream TF provider (v0.0.1 and v0.0.2).
2. Upgraded this provider to v0.0.1 as an initial baseline version
3. Re-enabled the upgrade-provider workflow in this repo
4. Added an optional input for the ref of the version of upgrade-provider to use in the workflow so we can test pre-release versions

Next step: Design an automated process from ci-mgmt to:

1. Cut a new version of the upstream tf provider.
2. Trigger the upgrade workflow on the branch of the PR.
3. Assert that:
   • The upgrade issue is created.
   • The upgreade PR is created.
   • The PR will close the issue.
   • The PR build passes.
4. Close the PR and issue (add resolution & assignee).