Potential performance regression for TPCH q18

### Describe the bug

While enabling `StringView` reading from Parquet in https://github.com/apache/datafusion/pull/13101 @Dandandan noticed a slight regression for TPCH 18 https://github.com/apache/datafusion/pull/13101#issuecomment-2437865910

here is the query
```sql
select
c_name,
c_custkey,
o_orderkey,
o_orderdate,
o_totalprice,
sum(l_quantity)
from
customer,
orders,
lineitem
where
o_orderkey in (
select
l_orderkey
from
lineitem
group by
l_orderkey having
sum(l_quantity) > 300
)
and c_custkey = o_custkey
and o_orderkey = l_orderkey
group by
c_name,
c_custkey,
o_orderkey,
o_orderdate,
o_totalprice
order by
o_totalprice desc,
o_orderdate;
```

### To Reproduce

To reproduce

Make data
```shell
# make the data and get to the correct location
cd datafusion/benchmarks
./bench.sh data tpch
cd data/tpch_sf1
```

Run query:
```
datafusion-cli -f ../../queries/q18.sql | grep Elapsed
Elapsed 0.088 seconds.
```

When StringView is enabled it seems like it is slightly slower

### Expected behavior

StringView should always be faster

### Additional context

I took a brief look at the flamegraphs -- it seems like one difference could be `BatchCoalescer::push_batch`


There is a special case for StringView here:
https://github.com/apache/datafusion/blob/6034be42808b43e3f48f6e58ec38cc35fa253abb/datafusion/physical-plan/src/coalesce/mod.rs#L117-L116

Here are the explain plans for the query before and after the change
- [q18-before.txt](https://github.com/user-attachments/files/17577287/q18-before.txt)
- [q18-after.txt](https://github.com/user-attachments/files/17577286/q18-after.txt)

Here are the flamegraphs for the query before/after the change
- 
-