CVE-2024-31995: zcap has incomplete expiration checks in capability chains.

When invoking a capability with a chain depth of 2, i.e., it is delegated directly from the root capability, the expires property is not properly checked against the current date or other date param. This can allow invocations outside of the original intended time period. A zcap still cannot be invoked without being able to use the associated private key material.