Update parsePCClientEventLog to output GrubState
Update parsePCClientEventLog to output GrubState

When using Loader == GRUB, parsePCClientEventLog will extract from
the event log: digests of files that GRUB reads in and the text of
commands GRUB runs.

google/go-tpm-tools,google/go-tpm-tools,google/go-tpm-tools