In sync tool, fix "existing PR" query: consider repository name

[dagood]

Fixes an error in the sync pipeline that occurred because two active PRs into branches named microsoft/main were happening at the same time, microsoft/go#1251 and microsoft/go-images#316:

https://dev.azure.com/dnceng/internal/_build/results?buildId=2477557&view=logs&j=881b2ec9-fc45-57ee-6456-bdd38ea7f007&t=a85e175a-b476-51c2-71e7-c3450accbe07&l=201

The GraphQL API doesn't have a filter for repository name, and the job got this data:

{
  "data": {
    "user": {
      "pullRequests": {
        "nodes": [
          {
            "title": "Update submodule to latest `master` in `microsoft/main`",
            "id": "PR_kwDOFG13585yf6nr",
            "number": 1251,
            "headRepositoryOwner": {
              "login": "microsoft"
            },
            "baseRepository": {
              "owner": {
                "login": "microsoft"
              }
            }
          },
          {
            "title": "Update submodule to latest `master` in `microsoft/main`",
            "id": "PR_kwDOF7mTR85yf6pG",
            "number": 316,
            "headRepositoryOwner": {
              "login": "microsoft"
            },
            "baseRepository": {
              "owner": {
                "login": "microsoft"
              }
            }
          }
        ]
      }
    }
  }
}

The sync code has a safeguard to make sure only 1 or 0 results were returned to make sure that it doesn't get mixed up. That was triggered and the sync pipeline failed safe:

expected 0/1 PR search result, found 2
failed to submit one or more PRs
=== Failed sync 2/2

#124 uncovered this issue because, for the first time, the synced branch names used in multiple repos overlapped.

This PR fixes it by adding an extra field that GraphQL should return from the query, nameWithOwner. (microsoft/go, microsoft/go-images.) It's used to filter the results down. I used https://docs.github.com/en/graphql/overview/explorer to find and try out this new field.

• This PR is not tested. I'll run the sync pipeline with this code after submitting the PR. (Release automation staging environment go#1091)
  • Triggered https://dev.azure.com/dnceng/internal/_build/results?buildId=2477749&view=results

[dagood]

It worked, in https://dev.azure.com/dnceng/internal/_build/results?buildId=2477749&view=results