Separate suppression status from kind

[ghost]

BACKGROUND

We currently have four values for suppression.kind: "suppressedInSource", "suppressedExternally", "underReview", and "suppressionRejected". You see that these really fall into two categories: "suppressedInSource" and "suppressedExternally" says how the result was suppressed, and underReview and suppressionRejected track the process of deciding whether the result should be suppressed.

Not only are these different in semantics, but they are different in "number": a result might be suppressed in multiple ways, but it is in only one status at a time.

NOTE: We had a similar situation with result.level, which original included both "severity" values like warning and error, and "status" values like open. So we split result.level into two properties, level and kind.

While we're at it, we tighten up the value names.

SCHEMA CHANGES

In the suppression object:

• In the kind property, restrict the valid values to "inSource" and "external".
• Add a property status of type string, optional, with valid values "accepted", "underReview" and "rejected", default: "accepted".