Add false positive info to protobuf

[rosecodym]

Description:

This PR adds false positive information to the Result protobuf message in anticipation of us tracking it as first-class secret metadata. We're not doing that yet (it's blocked behind #2643) but setting up the messages now means we'll be able to do it later with less of a code delta.

Checklist:

• Tests passing (make test-community)?
• Lint passing (make lint this requires golangci-lint)?

[ahrav]

question: Do you foresee a situation where multiple fields in this message will be set to true? I'm wondering if an enum would also do the trick.

[rosecodym]

potentially! i can also foresee us adding additional information to it down the road (e.g. what word from the list was actually matched). i think an enum would also work but it feels more constraining.