fix(ftd.http): replicate error response behaviour for data response

[siddhantk232]

For the errors response from server, ftd.http correctly prepends defined
variables with the fastn-module name provided through ftd.http-options.

The same thing is not done for data response. This PR fixes this.

E.g.

-- optional string $name:

-- ftd.text: $name
if: { name }

-- ftd.text: test
$on-click$: send-req()

-- ftd.http-options opts:
method: GET
fastn-module: fastn-test-multiauth/

-- void send-req():
ftd.http-options opts: $opts

ftd.http(
    "http://localhost:3000/test.json",
    opts
)

The response from the server (http://localhost:3000/test.json):

{
    "data": {
        "name": "spiderman"
    }
}

The ftd.text shows "spiderman" with this change.