feat(spark): implement StringView for SparkConcat

[aryan-212]

Which issue does this PR close?

• This PR is part of the Utf8View support epic. It adds Utf8View support in the Spark-compat layer.

Rationale for this change

In our internal project we're only suppporting Utf8View (because of design constraints) and the current implementation of SparkConcat only supports Utf8. The SparkConcat function should accept Utf8View and mixed string types in line with the main DataFusion concat. This PR adds that support and follows the same patterns as DataFusion’s concat.

Prevents errors like :

The type of Utf8 AND Utf8View of like physical should be same.
This issue was likely caused by a bug in DataFusion's code. Please help us to resolve this by filing a bug report in our issue tracker: https://github.com/apache/datafusion/issues

from a query like:-

select i_item_sk,
       item_info
from
  (select i_item_sk,
          CONCAT('Item: ', i_item_desc) as item_info
   from item) sub
where item_info LIKE 'Item: Electronic%'
order by 1;

What changes are included in this PR?

• Extend the type signature to accept Utf8View in addition to Utf8 and LargeUtf8 via TypeSignature::Variadic(vec![Utf8View, Utf8, LargeUtf8]) matching DataFusion’s concat.

• In return_field_from_args, compute the result type with precedence Utf8View > LargeUtf8 > Utf8.
  In spark_concat, handle Utf8View and LargeUtf8 in scalar paths (zero-argument and all-NULL).

Are these changes tested?

Yes.

• Unit tests: cargo test --package datafusion-spark function::string::concat::tests, including test_concat_utf8view.
• Sqllogictest: spark/string/concat.slt includes a “Utf8View: no extra CAST in plan” case that uses EXPLAIN and a temporary table to ensure no extra CASTs when using arrow_cast(..., 'Utf8View') with table columns.

Are there any user-facing changes?

• API: SparkConcat’s signature is extended to include Utf8View in the variadic list. No breaking changes.

used gpt to rephrase some of these points

[Weijun-H]

LGTM, thanks @aryan-212 👍

It is better to add some mixed type tests

# Test mixed types: Utf8View + Utf8
query T
SELECT concat(arrow_cast('hello', 'Utf8View'), ' world');
----
hello world

# Test all three types mixed together
query T
SELECT concat('a', arrow_cast('b', 'LargeUtf8'), arrow_cast('c', 'Utf8View'));
----
abc

[aryan-212]

Added them @Weijun-H, thanks for reviewing 🙇

[aryan-212]

@Jefffrey , made the required test changes. Please have a look 🙇