Add name for each query and mutation in Hub Go client

[mszostok]

Description

After bumping graphql-js dependency, the e2e tests are failing. After debugging, I detected that for all unnamed queries/mutations, the GraphQL API returns 400 status code. Unfortunately, I cannot detect how our CI on PR didn't detect that.

Changes proposed in this pull request:

• Add name for each query and mutation in Hub Go client

[pkosiec]

This is OK change, I was able to confirm the issue on our stage cluster. The response in GraphQL Playground is terrible:

query {
  interfaces {
    path
  }
}

results in:

{
  "data": {},
  "errors": [
    {} // empty error!
  ]
}

and

query Interfaces {
  interfaces {
    path
  }
}

in:

{
  "data": {
    "interfaces": [
      {
        "path": "cap.core.interface.runner.generic.run"
      },
      {
// (...)

IMHO we should handle the issue #334 really soon.

Also, on this PR I noticed another, very similar fail on integration tests:

  Timed out after 300.001s.
  Error: Unexpected non-nil/non-zero extra argument at index 1:
  	<*errors.withStack>: while executing query to fetch Hub Implementation: All attempts fail:
  #1: graphql: 

Another time empty error from GraphQL... I think we should spend more time on debugging this in a dedicated issue.