Extend `verify` command with Runner choosing

For unregister command we can choose a Runner to unregister by its name or URL and token. But unregister should not be used in cases, when verify --delete is used.

The problem is that verify is working globally and if used with --delete flag it will remove all found Runners, that are not able to connect with their GitLab installations. In most cases this is OK, but it will generate a problem when some GitLab installations may be unavailable (like temporary active development installations or installations available only in specific networks).

We should extend the verify command to allow it to choose a runner to verify (and eventually delete if --deleted was used) in the same way as unregister is doing this.

Successor of #2164 (closed)