[SPARK-25098] Trim the string when cast stringToTimestamp and stringToDate - ASF JIRA

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UDF ‘Cast’ will return NULL when input string starts/ends with special character, but hive doesn't.

For examle, we get hour from a string ends with a blank :

hive：

```
hive> SELECT CAST(' 2018-08-13' AS DATE);//starts with a blank
OK
2018-08-13

hive> SELECT HOUR('2018-08-13 17:20:07 );//ends with a blank
OK
17
```

spark-sql:

```
spark-sql> SELECT CAST(' 2018-08-13' AS DATE);//starts with a blank
NULL

spark-sql> SELECT HOUR('2018-08-13 17:20:07 );//ends with a blank
NULL
```

All of the following UDFs will be affected:
```
year
month
day
hour
minute
second
date_add
date_sub
```

relates to

SPARK-28023 Trim the string when cast string type to other types

SPARK-30000 Trim the string when cast string type to decimals

links to

[Github] Pull Request #22089 (bingbai0912)