We-worked model to remove resolver.

lookups are performed inline now. keeps things simpler, however it has a performance knock, so it's time to refine async building were possible.

datamodel/low/reference.go

@@ -1,13 +1,16 @@
 package low
 
-import "gopkg.in/yaml.v3"
+import (
+	"github.com/pb33f/libopenapi/index"
+	"gopkg.in/yaml.v3"
+)
 
 type HasNode interface {
 	GetNode() *yaml.Node
 }
 
 type Buildable[T any] interface {
-	Build(node *yaml.Node) error
+	Build(node *yaml.Node, idx *index.SpecIndex) error
 	*T
 }