osbuild: add partuuid into the partition struct

The partuuid is a uuid of a specific GPT partition as opposed to the ptuuid
which is associated with the partition table and filesystem uuid which
is associated with a filesystem on a partition.

The support for partuuid was introduced in osbuild 11, see this PR for
reference: https://github.com/osbuild/osbuild/pull/306

internal/osbuild/qemu_assembler.go

@@ -22,6 +22,7 @@ type QEMUPartition struct {
 	Size       uint64         `json:"size,omitempty"`
 	Type       *uuid.UUID     `json:"type,omitempty"`
 	Bootable   bool           `json:"bootable,omitempty"`
+	UUID       *uuid.UUID     `json:"uuid,omitempty"`
 	Filesystem QEMUFilesystem `json:"filesystem"`
 }