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

## What changes were proposed in this pull request?

**Hive** and **Oracle** trim the string when cast `stringToTimestamp` and `stringToDate`. this PR support this feature:
![image](https://user-images.githubusercontent.com/5399861/47979721-793b1e80-e0ff-11e8-97c8-24b10950ee9e.png)
![image](https://user-images.githubusercontent.com/5399861/47979725-7dffd280-e0ff-11e8-87d4-5767a00ed46e.png)

## How was this patch tested?

unit tests

Closes apache#22089

Closes apache#22943 from wangyum/SPARK-25098.

Authored-by: Yuming Wang <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: wangyum

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala

@@ -274,7 +274,7 @@ object DateTimeUtils {
   }
 
   /**
-   * Parses a given UTF8 date string to the corresponding a corresponding [[Long]] value.
+   * Trim and parse a given UTF8 date string to the corresponding a corresponding [[Long]] value.
    * The return type is [[Option]] in order to distinguish between 0L and null. The following
    * formats are allowed:
    *
@@ -311,7 +311,7 @@ object DateTimeUtils {
     val segments: Array[Int] = Array[Int](1, 1, 1, 0, 0, 0, 0, 0, 0)
     var i = 0
     var currentSegmentValue = 0
-    val bytes = s.getBytes
+    val bytes = s.trim.getBytes
     var j = 0
     var digitsMilli = 0
     var justTime = false
@@ -441,7 +441,7 @@ object DateTimeUtils {
   }
 
   /**
-   * Parses a given UTF8 date string to a corresponding [[Int]] value.
+   * Trim and parse a given UTF8 date string to a corresponding [[Int]] value.
    * The return type is [[Option]] in order to distinguish between 0 and null. The following
    * formats are allowed:
    *
@@ -459,7 +459,7 @@ object DateTimeUtils {
     val segments: Array[Int] = Array[Int](1, 1, 1)
     var i = 0
     var currentSegmentValue = 0
-    val bytes = s.getBytes
+    val bytes = s.trim.getBytes
     var j = 0
     while (j < bytes.length && (i < 3 && !(bytes(j) == ' ' || bytes(j) == 'T'))) {
       val b = bytes(j)

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/util/DateTimeUtilsSuite.scala

@@ -140,16 +140,10 @@ class DateTimeUtilsSuite extends SparkFunSuite {
     c = Calendar.getInstance()
     c.set(2015, 2, 18, 0, 0, 0)
     c.set(Calendar.MILLISECOND, 0)
-    assert(stringToDate(UTF8String.fromString("2015-03-18")).get ===
-      millisToDays(c.getTimeInMillis))
-    assert(stringToDate(UTF8String.fromString("2015-03-18 ")).get ===
-      millisToDays(c.getTimeInMillis))
-    assert(stringToDate(UTF8String.fromString("2015-03-18 123142")).get ===
-      millisToDays(c.getTimeInMillis))
-    assert(stringToDate(UTF8String.fromString("2015-03-18T123123")).get ===
-      millisToDays(c.getTimeInMillis))
-    assert(stringToDate(UTF8String.fromString("2015-03-18T")).get ===
-      millisToDays(c.getTimeInMillis))
+    Seq("2015-03-18", "2015-03-18 ", " 2015-03-18", " 2015-03-18 ", "2015-03-18 123142",
+      "2015-03-18T123123", "2015-03-18T").foreach { s =>
+      assert(stringToDate(UTF8String.fromString(s)).get === millisToDays(c.getTimeInMillis))
+    }
 
     assert(stringToDate(UTF8String.fromString("2015-03-18X")).isEmpty)
     assert(stringToDate(UTF8String.fromString("2015/03/18")).isEmpty)
@@ -214,9 +208,10 @@ class DateTimeUtilsSuite extends SparkFunSuite {
       c = Calendar.getInstance(tz)
       c.set(2015, 2, 18, 0, 0, 0)
       c.set(Calendar.MILLISECOND, 0)
-      checkStringToTimestamp("2015-03-18", Option(c.getTimeInMillis * 1000))
-      checkStringToTimestamp("2015-03-18 ", Option(c.getTimeInMillis * 1000))
-      checkStringToTimestamp("2015-03-18T", Option(c.getTimeInMillis * 1000))
+
+      Seq("2015-03-18", "2015-03-18 ", " 2015-03-18", " 2015-03-18 ", "2015-03-18T").foreach { s =>
+        checkStringToTimestamp(s, Option(c.getTimeInMillis * 1000))
+      }
 
       c = Calendar.getInstance(tz)
       c.set(2015, 2, 18, 12, 3, 17)