Extract sdk into its own lib

This had some side effects:

 - Have to add some utils from the kairos/machine modules, which IMHO
   should not be there, they should be here if the are generic enough
 - Dropping the sdk dir, just have the modules in the root dir

Signed-off-by: Itxaka <itxaka.garcia@spectrocloud.com>

state/machine.go

@@ -0,0 +1,10 @@
+package state
+
+type Machine struct {
+	BootArgs    []string
+	CloudConfig string
+}
+
+type Spec struct {
+	MachineSpec Machine
+}