multi: move node ann validation code to netann pkg

The `netann` package is a more appropriate place for this code to live.
Also, once the funding transaction code is moved out of the
`graph.Builder`, then no `lnwire` validation will occur in the `graph`
package.

graph/ann_validation.go

@@ -1,47 +0,0 @@
-package graph
-
-import (
-	"bytes"
-
-	"github.com/btcsuite/btcd/btcec/v2"
-	"github.com/btcsuite/btcd/chaincfg/chainhash"
-	"github.com/go-errors/errors"
-	"github.com/lightningnetwork/lnd/lnwire"
-)
-
-// ValidateNodeAnn validates the node announcement by ensuring that the
-// attached signature is needed a signature of the node announcement under the
-// specified node public key.
-func ValidateNodeAnn(a *lnwire.NodeAnnouncement) error {
-	// Reconstruct the data of announcement which should be covered by the
-	// signature so we can verify the signature shortly below
-	data, err := a.DataToSign()
-	if err != nil {
-		return err
-	}
-
-	nodeSig, err := a.Signature.ToSignature()
-	if err != nil {
-		return err
-	}
-	nodeKey, err := btcec.ParsePubKey(a.NodeID[:])
-	if err != nil {
-		return err
-	}
-
-	// Finally ensure that the passed signature is valid, if not we'll
-	// return an error so this node announcement can be rejected.
-	dataHash := chainhash.DoubleHashB(data)
-	if !nodeSig.Verify(dataHash, nodeKey) {
-		var msgBuf bytes.Buffer
-		if _, err := lnwire.WriteMessage(&msgBuf, a, 0); err != nil {
-			return err
-		}
-
-		return errors.Errorf("signature on NodeAnnouncement(%x) is "+
-			"invalid: %x", nodeKey.SerializeCompressed(),
-			msgBuf.Bytes())
-	}
-
-	return nil
-}