Recommended refactors

- make sure spec sets new cache dir
- move clean out of api
- capture warewulfconf.Paths.Cachedir+"/warewulf" in once place
- split Clean() into multiple functions
- remove WriteFileAbs

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

internal/pkg/config/buildconfig.go.in

@@ -1,5 +1,9 @@
 package config
 
+import (
+	"path"
+)
+
 var ConfigFile = "@SYSCONFDIR@/warewulf/warewulf.conf"
 
 type BuildConfig struct {
@@ -43,3 +47,11 @@ type WarewulfConf struct {
 	DataStore         string `yaml:"datastore" default:"@DATADIR@"`
 	GrubBoot          bool   `yaml:"grubboot" default:"false"`
 }
+
+func (paths BuildConfig) OciBlobCachedir() string {
+	return path.Join(paths.Cachedir, "warewulf")
+}
+
+func (paths BuildConfig) OverlayProvisiondir() string {
+	return path.Join(paths.WWProvisiondir, "overlays")
+}