`zed expand <...> --json` does not match the expected schema

[authzed]

`zed expand <...> --json` does not match the expected schema

[williamdclt]

It also seems that for intermediate nodes, zed returns the operation attribute as something like "OPERATION_EXCLUSION" rather than 2 like the API

[jzelinskie]

We actually hadn't considered making the zed --json flag compatible with rest gateway, but it seems obvious in retrospect.

Looks like this is a difference between just calling protojson on the result vs how grpc gateway calls protojson.

I could see two ways of fixing this:

1. making the --json flag actually perform a REST request instead of gRPC
2. try make both sources generate the same output

I think I'm leaning towards the first option as just dumping the request with protojson was kinda a hack so we could use jq before we ever had an HTTP API.