Initial work to add an in-memory layer on top of the TxStore

common/txmgr/broadcaster.go

@@ -695,7 +695,7 @@ func (eb *Broadcaster[CHAIN_ID, HEAD, ADDR, TX_HASH, BLOCK_HASH, SEQ, FEE]) next
 	defer cancel()
 	etx := &txmgrtypes.Tx[CHAIN_ID, ADDR, TX_HASH, BLOCK_HASH, SEQ, FEE]{}
 	if err := eb.txStore.FindNextUnstartedTransactionFromAddress(ctx, etx, fromAddress, eb.chainID); err != nil {
-		if errors.Is(err, sql.ErrNoRows) {
+		if errors.Is(err, sql.ErrNoRows) || errors.Is(err, ErrTxnNotFound) {
 			// Finish. No more transactions left to process. Hoorah!
 			return nil, nil
 		}