[SPARK-31874][SQL] Use FastDateFormat as the legacy fractional formatter

### What changes were proposed in this pull request?
1. Replace `SimpleDateFormat` by `FastDateFormat` as the legacy formatter of `FractionTimestampFormatter`.
2. Optimise `LegacyFastTimestampFormatter` for `java.sql.Timestamp` w/o fractional part.

### Why are the changes needed?
1. By default `HiveResult`.`hiveResultString` retrieves timestamps values as instances of `java.sql.Timestamp`, and uses the legacy parser `SimpleDateFormat` to convert the timestamps to strings. After the fix #28024, the fractional formatter and its companion - legacy formatter `SimpleDateFormat` are created per every value. By switching from `LegacySimpleTimestampFormatter` to `LegacyFastTimestampFormatter`, we can utilize the internal cache of `FastDateFormat`, and avoid parsing the default pattern `yyyy-MM-dd HH:mm:ss`.
2. The second change in the method `def format(ts: Timestamp): String` of `LegacyFastTimestampFormatter` is needed to optimize the formatter for patterns without the fractional part and avoid conversions to microseconds.

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
By existing tests in `TimestampFormatter`.

Closes #28678 from MaxGekk/fastdateformat-as-legacy-frac-formatter.

Authored-by: Max Gekk <max.gekk@gmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
(cherry picked from commit 47dc332)
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

Author: MaxGekk

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

@@ -121,6 +121,7 @@ class FractionTimestampFormatter(zoneId: ZoneId)
     TimestampFormatter.defaultPattern,
     zoneId,
     TimestampFormatter.defaultLocale,
+    LegacyDateFormats.FAST_DATE_FORMAT,
     needVarLengthSecondFraction = false) {
 
   @transient
@@ -203,7 +204,11 @@ class LegacyFastTimestampFormatter(
   }
 
   override def format(ts: Timestamp): String = {
-    format(fromJavaTimestamp(ts))
+    if (ts.getNanos == 0) {
+      fastDateFormat.format(ts)
+    } else {
+      format(fromJavaTimestamp(ts))
+    }
   }
 
   override def format(instant: Instant): String = {