[SPARK-27922][SQL][PYTHON][TESTS] Convert and port 'natural-join.sql' into UDF test base

[manuzhang]

What changes were proposed in this pull request?

This PR adds some tests converted from natural-join.sql to test UDFs following the combination guide in SPARK-27921.

Diff results comparing to `natural-join.sql`

diff --git a/sql/core/src/test/resources/sql-tests/results/udf/udf-natural-join.sql.out b/sql/core/src/test/resources/sql-tests/results/udf/udf-natural-join.
sql.out
index 43f2f9a..53ef177 100644
--- a/sql/core/src/test/resources/sql-tests/results/udf/udf-natural-join.sql.out
+++ b/sql/core/src/test/resources/sql-tests/results/udf/udf-natural-join.sql.out
@@ -27,7 +27,7 @@ struct<>


 -- !query 2
-SELECT * FROM nt1 natural join nt2 where k = "one"
+SELECT * FROM nt1 natural join nt2 where udf(k) = "one"
 -- !query 2 schema
 struct<k:string,v1:int,v2:int>
 -- !query 2 output
@@ -36,7 +36,7 @@ one   1       5


 -- !query 3
-SELECT * FROM nt1 natural left join nt2 order by v1, v2
+SELECT * FROM nt1 natural left join nt2 where k <> udf("") order by v1, v2
 -- !query 3 schema
diff --git a/sql/core/src/test/resources/sql-tests/results/udf/udf-natural-join.sql.out b/sql/core/src/test/resources/sql-tests/results/udf/udf-natural-join.
sql.out
index 43f2f9a..53ef177 100644
--- a/sql/core/src/test/resources/sql-tests/results/udf/udf-natural-join.sql.out
+++ b/sql/core/src/test/resources/sql-tests/results/udf/udf-natural-join.sql.out
@@ -27,7 +27,7 @@ struct<>


 -- !query 2
-SELECT * FROM nt1 natural join nt2 where k = "one"
+SELECT * FROM nt1 natural join nt2 where udf(k) = "one"
 -- !query 2 schema
 struct<k:string,v1:int,v2:int>
 -- !query 2 output
@@ -36,7 +36,7 @@ one   1       5


 -- !query 3
-SELECT * FROM nt1 natural left join nt2 order by v1, v2
+SELECT * FROM nt1 natural left join nt2 where k <> udf("") order by v1, v2
 -- !query 3 schema
 struct<k:string,v1:int,v2:int>

How was this patch tested?

Tested as guided in SPARK-27921.

[manuzhang]

@HyukjinKwon please help review

[HyukjinKwon]

ok to test

[HyukjinKwon]

LGTM if tests pass

[SparkQA]

Test build #107420 has finished for PR 25088 at commit a20eff0.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[HyukjinKwon]

Merged to master.