tests/int: Add separate resource cleanup step

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>

tests/integration/Makefile

@@ -17,6 +17,14 @@ test-azure:
 test-gcp:
 	$(MAKE) test PROVIDER_ARG="-provider gcp"
 
+destroy:
+	go test -timeout $(TEST_TIMEOUT) -v ./ $(GO_TEST_ARGS) $(PROVIDER_ARG) -destroy-only
+
+destroy-azure:
+	$(MAKE) destroy PROVIDER_ARG="-provider azure"
+
+destroy-gcp:
+	$(MAKE) destroy PROVIDER_ARG="-provider gcp"
 
 sops-check:
 ifeq ($(shell which sops),)