Return Service Name in GetCheckResults API response

Currently, there is no Service Name returned for GetCheckResults call. We need to return it as this endpoint will be used by FE to show Failed checks.

Current response:

  {
    summary: 'Newer version of Percona Server for MySQL is available',
    description: 'Current version is 5.7.30, the latest available version is 5.7.33.',
    severity: 'SEVERITY_WARNING',
    labels: { current: '5.7.30', latest: '5.7.33' },
    read_more_url: 'https://www.percona.com/doc/percona-server/LATEST/release-notes/release-notes_index.html'
  },

How to test?
1.  Add a service to be monitored using pmm-admin using the `--service-name` flag to name the service
2. Run checks
3. Call this API endpoint /v1/management/SecurityChecks/GetCheckResults  it should contain a new field service_name

FB:    https://github.com/Percona-Lab/pmm-submodules/pull/1838

Note: UI tests failure in the FB might be un-related, will check later