[SPARK-28287][SQL][PYTHON][TESTS] Convert and port 'udaf.sql' into UDF test base

## What changes were proposed in this pull request?

This PR adds some tests converted from 'udaf.sql' to test UDFs

<details><summary>Diff comparing to 'udaf.sql'</summary>
<p>

```diff
diff --git a/sql/core/src/test/resources/sql-tests/results/udaf.sql.out b/sql/core/src/test/resources/sql-tests/results/udf/udf-udaf.sql.out
index f4455bb..e1747f4 100644
--- a/sql/core/src/test/resources/sql-tests/results/udaf.sql.out
+++ b/sql/core/src/test/resources/sql-tests/results/udf/udf-udaf.sql.out
 -3,6 +3,8

 -- !query 0
+-- This test file was converted from udaf.sql.
+
 CREATE OR REPLACE TEMPORARY VIEW t1 AS SELECT * FROM VALUES
 (1), (2), (3), (4)
 as t1(int_col1)
 -21,15 +23,15  struct<>

 -- !query 2
-SELECT default.myDoubleAvg(int_col1) as my_avg from t1
+SELECT default.myDoubleAvg(udf(int_col1)) as my_avg, udf(default.myDoubleAvg(udf(int_col1))) as my_avg2, udf(default.myDoubleAvg(int_col1)) as my_avg3 from t1
 -- !query 2 schema
-struct<my_avg:double>
+struct<my_avg:double,my_avg2:double,my_avg3:double>
 -- !query 2 output
-102.5
+102.5  102.5   102.5

 -- !query 3
-SELECT default.myDoubleAvg(int_col1, 3) as my_avg from t1
+SELECT default.myDoubleAvg(udf(int_col1), udf(3)) as my_avg from t1
 -- !query 3 schema
 struct<>
 -- !query 3 output
 -46,12 +48,12  struct<>

 -- !query 5
-SELECT default.udaf1(int_col1) as udaf1 from t1
+SELECT default.udaf1(udf(int_col1)) as udaf1, udf(default.udaf1(udf(int_col1))) as udaf2, udf(default.udaf1(int_col1)) as udaf3 from t1
 -- !query 5 schema
 struct<>
 -- !query 5 output
 org.apache.spark.sql.AnalysisException
-Can not load class 'test.non.existent.udaf' when registering the function 'default.udaf1', please make sure it is on the classpath; line 1 pos 7
+Can not load class 'test.non.existent.udaf' when registering the function 'default.udaf1', please make sure it is on the classpath; line 1 pos 94

 -- !query 6
```

</p>
</details>

## How was this patch tested?

Tested as guided in SPARK-27921.

Closes apache#25194 from vinodkc/br_Fix_SPARK-27921_3.

Authored-by: Vinod KC <[email protected]>
Signed-off-by: HyukjinKwon <[email protected]>

Author: vinodkc

sql/core/src/test/resources/sql-tests/inputs/udf/udf-udaf.sql

@@ -0,0 +1,18 @@
+    -- This test file was converted from udaf.sql.
+
+CREATE OR REPLACE TEMPORARY VIEW t1 AS SELECT * FROM VALUES
+(1), (2), (3), (4)
+as t1(int_col1);
+
+CREATE FUNCTION myDoubleAvg AS 'test.org.apache.spark.sql.MyDoubleAvg';
+
+SELECT default.myDoubleAvg(udf(int_col1)) as my_avg, udf(default.myDoubleAvg(udf(int_col1))) as my_avg2, udf(default.myDoubleAvg(int_col1)) as my_avg3 from t1;
+
+SELECT default.myDoubleAvg(udf(int_col1), udf(3)) as my_avg from t1;
+
+CREATE FUNCTION udaf1 AS 'test.non.existent.udaf';
+
+SELECT default.udaf1(udf(int_col1)) as udaf1, udf(default.udaf1(udf(int_col1))) as udaf2, udf(default.udaf1(int_col1)) as udaf3 from t1;
+
+DROP FUNCTION myDoubleAvg;
+DROP FUNCTION udaf1;

sql/core/src/test/resources/sql-tests/results/udf/udf-udaf.sql.out

@@ -0,0 +1,72 @@
+-- Automatically generated by SQLQueryTestSuite
+-- Number of queries: 8
+
+
+-- !query 0
+-- This test file was converted from udaf.sql.
+
+CREATE OR REPLACE TEMPORARY VIEW t1 AS SELECT * FROM VALUES
+(1), (2), (3), (4)
+as t1(int_col1)
+-- !query 0 schema
+struct<>
+-- !query 0 output
+
+
+
+-- !query 1
+CREATE FUNCTION myDoubleAvg AS 'test.org.apache.spark.sql.MyDoubleAvg'
+-- !query 1 schema
+struct<>
+-- !query 1 output
+
+
+
+-- !query 2
+SELECT default.myDoubleAvg(udf(int_col1)) as my_avg, udf(default.myDoubleAvg(udf(int_col1))) as my_avg2, udf(default.myDoubleAvg(int_col1)) as my_avg3 from t1
+-- !query 2 schema
+struct<my_avg:double,my_avg2:double,my_avg3:double>
+-- !query 2 output
+102.5	102.5	102.5
+
+
+-- !query 3
+SELECT default.myDoubleAvg(udf(int_col1), udf(3)) as my_avg from t1
+-- !query 3 schema
+struct<>
+-- !query 3 output
+org.apache.spark.sql.AnalysisException
+Invalid number of arguments for function default.myDoubleAvg. Expected: 1; Found: 2; line 1 pos 7
+
+
+-- !query 4
+CREATE FUNCTION udaf1 AS 'test.non.existent.udaf'
+-- !query 4 schema
+struct<>
+-- !query 4 output
+
+
+
+-- !query 5
+SELECT default.udaf1(udf(int_col1)) as udaf1, udf(default.udaf1(udf(int_col1))) as udaf2, udf(default.udaf1(int_col1)) as udaf3 from t1
+-- !query 5 schema
+struct<>
+-- !query 5 output
+org.apache.spark.sql.AnalysisException
+Can not load class 'test.non.existent.udaf' when registering the function 'default.udaf1', please make sure it is on the classpath; line 1 pos 94
+
+
+-- !query 6
+DROP FUNCTION myDoubleAvg
+-- !query 6 schema
+struct<>
+-- !query 6 output
+
+
+
+-- !query 7
+DROP FUNCTION udaf1
+-- !query 7 schema
+struct<>
+-- !query 7 output
+