Add the positive-path host-based tests for the shared GptLib parser
(extracted as part of the parser security hardening), ensuring the
tightened checks in PartitionValidGptTable(), PartitionCheckGptEntry()
and PartitionRestoreGptTable() do not falsely reject well-formed GPTs.
The tests run against an in-memory mock disk and cover accepted
primary/backup headers, boundary but legal header/entry sizes, correct
entry-status flagging on valid entries, and primary/backup restore
round-trips.
Signed-off-by: Richard Lyu <richard.lyu@suse.com>
