Add method to get field ids for a proto message class

[gino-m]

@rfontanarosa FYI

Usage:

import {registry} from '@ground/lib';
import {GroundProtos} from '@ground/proto';

import Pb = GroundProtos.google.ground.v1beta1;
const s = registry.getFieldIds(Pb.Survey);
const survey = {
  [s.name]: 'Survey name',
  [s.description]: 'Description something something',
  ...
};

[gino-m]

@rfontanarosa I still can't get this to work. For some reason when adding a new import of GroundProtos or registry, GroundProtos gets replaced with an invalid representation containing the following:

{
  "google": {
    "protobuf": {
      "NullValue": {
        "NULL_VALUE": 0
      }
    },
    "events": {
      "cloud": {
        "firestore": {
          "v1": {}
        }
      }
    },
    "type": {}
  }
}

None of these fields are in the ground-protos.js or ground-protos.d.ts, so I suspect either something is overriding the google namespace in that module.

[gino-m]

@rfontanarosa It seems there was a collision with google.* protos. Renaming proto packages to ground.* to fix. @shobhitagarwal1612 @sufyanAbbasi @scolsen A fix will also be needed on Android when we upgrade the proto dep, but the protos should be wire compatible even without.