Avoid row filter check when no constraints

The function call overhead is expensive!

This makes count(*) on the census data 175ms instead
of 225ms, while not significantly impacting other use cases.

parquet/parquet_cursor.cc

@@ -706,7 +706,7 @@ start:
 
   rowsLeftInRowGroup--;
   rowId++;
-  if(!currentRowSatisfiesFilter())
+  if(constraints.size() > 0 && !currentRowSatisfiesFilter())
     goto start;
 }