Add support for UKI in PCR4

[travier]

Support passing a UKI for PCR4 computation in https://github.com/trusted-execution-clusters/compute-pcrs/blob/main/lib/src/tpmevents/compute.rs. See: https://github.com/trusted-execution-clusters/compute-pcrs/pull/33/changes#diff-f8cd0fc9fbbb8070d21e750fd63b08f122bc699b3589aedb677c63c1b65c2234