Get a list of the container virtual registry upstreams

Overview:

• Add virtualRegistriesContainerUpstreams field under the group.
• Add search by upstream name functionality

Proposed query:

query {
  group(fullPath: "<group-path>") {
    virtualRegistriesContainerUpstreams(upstreamName: "test", first: 10) {
      count
      nodes {
        id
        name
        registriesCount
      }
      pageInfo {
        endCursor
        startCursor
        hasPreviousPage
        hasNextPage
      }
    }
  }
}

Maven reference: !205320 (merged)