core: make txpool free space calculation more accurate (#22933)

core/tx_pool.go

@@ -595,7 +595,7 @@ func (pool *TxPool) add(tx *types.Transaction, local bool) (replaced bool, err e
 		return false, err
 	}
 	// If the transaction pool is full, discard underpriced transactions
-	if uint64(pool.all.Count()+numSlots(tx)) > pool.config.GlobalSlots+pool.config.GlobalQueue {
+	if uint64(pool.all.Slots()+numSlots(tx)) > pool.config.GlobalSlots+pool.config.GlobalQueue {
 		// If the new transaction is underpriced, don't accept it
 		if !isLocal && pool.priced.Underpriced(tx) {
 			log.Trace("Discarding underpriced transaction", "hash", hash, "price", tx.GasPrice())