…1284)

* [SPARK-31008][SQL] Support json_array_length function

### What changes were proposed in this pull request?
At the moment we do not have any function to compute length of JSON array directly.
I propose a  `json_array_length` function which will return the length of the outermost JSON array.

- This function will return length of the outermost JSON array, if JSON array is valid.
```

scala> spark.sql("select json_array_length('[1,2,3,[33,44],{\"key\":[2,3,4]}]')").show
+--------------------------------------------------+
|json_array_length([1,2,3,[33,44],{"key":[2,3,4]}])|
+--------------------------------------------------+
|                                                 5|
+--------------------------------------------------+

scala> spark.sql("select json_array_length('[[1],[2,3]]')").show
+------------------------------+
|json_array_length([[1],[2,3]])|
+------------------------------+
|                             2|
+------------------------------+

```
- In case of any other valid JSON string, invalid JSON string or null array or `NULL` input , `NULL` will be returned.
```
scala> spark.sql("select json_array_length('')").show
+-------------------+
|json_array_length()|
+-------------------+
|               null|
+-------------------+
```

### Why are the changes needed?

- As mentioned in JIRA, this function is supported by presto, postgreSQL, redshift, SQLite, MySQL, MariaDB, IBM DB2.

- for better user experience and ease of use.

```
Performance Result for Json array - [1, 2, 3, 4]

Intel(R) Core(TM) i7-9750H CPU  2.60GHz
JSON functions:                           Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
json_array_length                                  7728           7762          53          1.3         772.8       1.0X
size+from_json                                    12739          12895         199          0.8        1273.9       0.6X

```

### Does this PR introduce any user-facing change?
Yes, now users can get length of a json array by using `json_array_length`.

### How was this patch tested?
Added UT.

Closes #27759 from iRakson/jsonArrayLength.

Authored-by: iRakson <raksonrakesh@gmail.com>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

(cherry picked from commit 71022d7)