cnct+lnwl+hswc: use lntypes.Preimage for witness beacon

breacharbiter_test.go

@@ -1548,10 +1548,7 @@ func createInitChannels(revocationWindow int) (*lnwallet.LightningChannel, *lnwa
 		Packager:                channeldb.NewChannelPackager(shortChanID),
 	}
 
-	pCache := &mockPreimageCache{
-		// hash -> preimage
-		preimageMap: make(map[[32]byte][]byte),
-	}
+	pCache := newMockPreimageCache()
 
 	aliceSigner := &mockSigner{aliceKeyPriv}
 	bobSigner := &mockSigner{bobKeyPriv}