refactor(cosmos-data-layer): make GeneralArgs a union of specific args
refactor(cosmos-data-layer): make GeneralArgs a union of specific args

As GeneralArgs seems to have been introduced as `IResolver`s input args are
hardcoded to `any` in `makeSchemaExecutable`, we have to
narrow down the type of the input manually. Let's typecheck that the input is
one of the possible inputs we actually want to work with.

dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui