feat: add finding_class and indicator fields in Finding (#579)

* feat: add finding_class and indicator fields in Finding

finding_class field is added in order to help our customer to quickly identify and categorize the different findings (threat, vulnerability, misconfiguration, ...). And indicator field is generated to indicate the domain and IP addresses that is causing the threat.

PiperOrigin-RevId: 386975549

Source-Link: googleapis/googleapis@5bf36f2

Source-Link: googleapis/googleapis-gen@b9ab677

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