Include ci-mgmt ref in the makefile

[danielrbradley]

Use make ci-mgmt focused on re-generating having updated ci-mgmt config rather than for pulling the latest changes.

For updating to the latest workflows, we still use the central CI process because it also runs migrations on the code.

When generating the a provider's files in CI, we could include the current ci-mgmt ref in the makefile for when calling ci-mgmt. This would make the make ci-mgmt command re-generate using the same version of ci-mgmt as was previously used.

For example:

 	rm .github/workflows/*.yml # Copied from update-workflows.yml
-	go run github.com/pulumi/ci-mgmt/provider-ci@master generate \
+	go run github.com/pulumi/ci-mgmt/provider-ci@eebcf4ba8bf704ae3735dd2e42e9f320cd9e0c7c generate \
 		--name pulumi/pulumi-$(PACK) \
 		--out . \