use yaml/v3 and don't export Nodes

introduced wwbool and don't export
Nodes and NodeConfs. This requires new
explict Yaml (un)marshaling as the standard
marshaller won't touch these fields

Signed-off-by: Christian Goll <cgoll@suse.com>

internal/pkg/config/root.go

@@ -17,7 +17,7 @@ import (
 
 	"github.com/creasty/defaults"
 	"github.com/warewulf/warewulf/internal/pkg/wwlog"
-	"gopkg.in/yaml.v2"
+	"gopkg.in/yaml.v3"
 )
 
 var cachedConf RootConf