Enable the `GraphQL/FieldMethod` cop

Follow-up of !74789 (diffs).

• 'app/graphql/types/ci/job_type.rb'
• 'app/graphql/types/merge_request_type.rb'
• 'app/graphql/types/metrics/dashboards/annotation_type.rb'
• 'app/graphql/types/packages/package_details_type.rb'
• 'app/graphql/types/project_type.rb'
• 'ee/app/graphql/types/dast/profile_type.rb'
• 'ee/app/graphql/types/dast_site_validation_type.rb'
• 'ee/app/graphql/types/group_release_stats_type.rb'
• 'ee/app/graphql/types/incident_management/oncall_rotation_type.rb'