treewide: introduce osbase package and move things around

All except localregistry moved from metropolis/pkg to osbase,
localregistry moved to metropolis/test as its only used there anyway.

Change-Id: If1a4bf377364bef0ac23169e1b90379c71b06d72
Reviewed-on: https://review.monogon.dev/c/monogon/+/3079
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
diff --git a/metropolis/node/build/mkerofs/main.go b/metropolis/node/build/mkerofs/main.go
index ac0042a..b5d5568 100644
--- a/metropolis/node/build/mkerofs/main.go
+++ b/metropolis/node/build/mkerofs/main.go
@@ -30,7 +30,7 @@
 	"strings"
 
 	"source.monogon.dev/metropolis/node/build/fsspec"
-	"source.monogon.dev/metropolis/pkg/erofs"
+	"source.monogon.dev/osbase/erofs"
 )
 
 func (spec *entrySpec) writeRecursive(w *erofs.Writer, pathname string) {