Implement CLI for ingested codeowners

[eseliger]

'src codeowners' is a tool that manages ingested code ownership data in a Sourcegraph instance.

Usage:

        src codeowners command [command options]

The commands are:

        get     returns the codeowners file for a repository, if exists
        create  create a codeowners file
        update  update a codeowners file
        delete  delete a codeowners file

Use "src codeowners [command] -h" for more information about a command.

Requires https://github.com/sourcegraph/sourcegraph/pull/48584.

Closes https://github.com/sourcegraph/sourcegraph/issues/47823.

Test plan

Verified with the new backend endpoints.

[leonore]

spotted a mismatch with main!

[leonore]

I think this isn't up to date with main anymore, it takes a slice (just in case we wanted an admin UI with it)

go run ./cmd/src codeowners delete -repo 'github.com/leonore/sourcegraph-test'
GraphQL errors: 2 errors occurred:
	* {
  "locations": [
    {
      "column": 24,
      "line": 4
    }
  ],
  "message": "Unknown argument \"repositories\" on field \"deleteCodeownersFiles\" of type \"Mutation\"."
}
	* {
  "locations": [
    {
      "column": 2,
      "line": 4
    }
  ],
  "message": "Field \"deleteCodeownersFiles\" argument \"repositoryIDs\" of type \"[Int!]!\" is required but not provided."
}
exit status 1

[eseliger]

did you try it as of https://github.com/sourcegraph/sourcegraph/pull/48584?

[leonore]

tested on latest main!