When a resource fails to initialize (i.e., it is successfully created,
but fails to transition to a fully-initialized state), and a user
subsequently runs `pulumi update` without changing that resource, our
CLI will fail to warn the user that this resource is not initialized.
This commit begins the process of allowing our CLI to report this by
storing a list of initialization errors in the checkpoint.
This commit adds CLI support for resource providers to provide partial
state upon failure. For resource providers that model resource
operations across multiple API calls, the Provider RPC interface can now
accomodate saving bags of state for resource operations that failed.
This is a common pattern for Terraform-backed providers that try to do
post-creation steps on resource as part of Create or Update resource
operations.
