Refactor service classes to use createServicePolicy

A previous commit added a `createServicePolicy` function to
`controller-utils`. This allows us to refactor the following service
classes which make use of a Cockatiel policy by replacing boilerplace
code with a simple function call:

- `CodefiV2` in `assets-controllers`
- `ClientConfigApiService` in `remote-feature-flag-controller`

Note that other service modules that do not yet make use of a Cockatiel
policy have not been updated to use `createServicePolicy`. We would need
to upgrade these areas to use the latest service object pattern we've
established.

packages/assets-controllers/package.json

@@ -66,7 +66,6 @@
     "@types/uuid": "^8.3.0",
     "async-mutex": "^0.5.0",
     "bn.js": "^5.2.1",
-    "cockatiel": "^3.1.2",
     "immer": "^9.0.6",
     "lodash": "^4.17.21",
     "multiformats": "^13.1.0",