JWT `claims_map` does not work when `claims_format` is `stringified_json`

### Version Information
Server Version: v2.2.2

### Environment
Cloud

### What is the expected behaviour?
`claims_map` with valid JSONPaths can be used when `claims_format` is `stringified_json`

### Keywords
jwt, claims_map, claims_format, stringified_json, cognito, jsonpath

### What is the current behaviour?

When JWT `claims_format` is `stringified_json`, you are not able to specify a `claims_map` with JSON Paths. If you do, you get the following error when making a query or mutation:

```
JWT claim from claims_map, x-hasura-user-id not found
```

### How to reproduce the issue?
1. Set the `HASURA_GRAPHQL_JWT_SECRET` environmental variable to:
```
{
"type": "RS256",
"jwk_url": "https:///.well-known/jwks.json",
"issuer": "https://",
"claims_namespace": "test",
"claims_format": "stringified_json",
"claims_map": {
"x-hasura-user-id": { "path": "$.test.user_id" },
"x-hasura-default-role": { "path": "$.test.default_role", "default": "user" },
"x-hasura-allowed-roles": { "path": "$.test.roles", "default": ["user"] }
},
"header": { "type": "Authorization" }
}
```
2. Attempt to make a query/mutation

### Any possible solutions?

Sorry, no!

### Can you identify the location in the source code where the problem exists?

No :(

### If the bug is confirmed, would you be willing to submit a PR?

Unfortunately not