Fix GraphQL errors with __typename

[mattjohnsonpint]

Fixes HYP-1066

Also further improved error handling, and added support for a HYPERMODE_TRACE environment variable to emit super detailed trace info to the GraphQL response. (That will be only used for detailed debugging purposes.)

[linear]

HYP-1066 Runtime doesn't handle `__typename` in inbound GraphQL request

GraphQL allows you to request __typename, a meta field, at any point in a query to get the name of the object type at that point.

Runtime gives:

{
    "errors": [
        {
            "message": "Internal Error"
        }
    ],
    "data": null
}