The GPT partition layout defines the type of the partition using a
UUID[1]. The type of the partition is not related to the underlying
filesystem but to its functionality: rootfs, home, var, swap, esp...
The UUID 4f68bce3-e8cd-4db1-96e7-fbcaf984b709 defines the root partition
(/), the UUID 933ac7e1-2eb4-4f13-b844-0e14e2aef915 defines the home
partition (/home), the UUID 4d21b016-b534-45c2-a9fb-5c16e091fd2d defines
the variable partition (/var)... Also, the UUIDs may vary depending on
the architecture (x86, x86_64, arm or aarch64).
KPMcore guesses the type depending on the underlying filesystem.
This commit enables the setting of a more specific GPT type if it is
specified through the method Partition::setType(). It falls back to the
previous guess type if the type is left unset.
[1]: https://systemd.io/DISCOVERABLE_PARTITIONS/