CVE-2024-55655: sigstore has insufficient validation of integration timestamp during verification

Versions of sigstore-python newer than 2.0.0 but prior to 3.6.0 perform insufficient validation of the “integration time” present in “v2” and “v3” bundles during the verification flow: the “integration time” is verified if a source of signed time (such as an inclusion promise) is present, but is otherwise trusted if no source of signed time is present.

This does not affect “v1” bundles, as the “v1” bundle format always requires an inclusion promise.