Add default_label_name to JSON output of buf registry module info

[doriable]

This adds information for the default label name of a module
to the JSON output of buf registry module info. The text output
remains unchanged.

$ buf registry module info buf.build/bufbuild/registry
Name                         Create Time
buf.build/bufbuild/registry  2023-10-27T20:23:20Z

$ buf registry module info buf.build/bufbuild/registry --format json | jq .
{
  "id": "11bdb5abfb544d54b2a3b7a354a07112",
  "remote": "buf.build",
  "owner": "bufbuild",
  "name": "registry",
  "create_time": "2023-10-27T20:23:20.396779Z",
  "state": "MODULE_STATE_ACTIVE",
  "default_label_name": "main"
}

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf CI / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Oct 7, 2024, 6:33 PM