Checkout Block: Surface errors from Cart Routes/batch

[mikejolley]

If a cart route returns an error, for example, select-shipping-rate, the error is not surfaced during checkout. We need to collect and aggregate all errors returned from the API, group by error ID (to prevent duplicates) and then surface errors in the correct notice containers.

This PR introduces new Notice containers, so we can use those to surface errors in particular places by mapping error codes to contexts in the client.

See #5971 (comment) for context.