Introduce a destroy-only mode in the test runner to run terraform
destroy for the respective cloud provider configurations. This can be
used to destroy cloud resources without going through the whole
provision-test process.
Add a new step in github actions workflow to run the test binary in
destoy-only mode at the very end irrespective of the result of the
previous steps. This ensures that the infrastructure is always
destroyed, even if the CI job is cancelled.
Signed-off-by: Sunny <darkowlzz@protonmail.com>
