fix(fields): use read commit isolation level in trigger (#8410)

# Which Problems Are Solved

If the processing time of serializable transactions in the fields
handler take too long, the next iteration can fail.

# How the Problems Are Solved

Changed the isolation level of the current states query to Read Commited

internal/eventstore/handler/v2/field_handler.go

@@ -97,7 +97,7 @@ func (h *FieldHandler) processEvents(ctx context.Context, config *triggerConfig)
 		defer cancel()
 	}
 
-	tx, err := h.client.BeginTx(txCtx, nil)
+	tx, err := h.client.BeginTx(txCtx, &sql.TxOptions{Isolation: sql.LevelReadCommitted})
 	if err != nil {
 		return false, err
 	}