More formats support by additional conversions for FromUnixTime

[firestarman]

Support format yyyyMMdd for GpuFromUnixTime

scala> Seq(System.currentTimeMillis()/1000).toDF("dt").repartition(1).selectExpr("*", "from_unixtime(dt, 'yyyyMMdd')").show
23/12/04 12:51:28 WARN GpuOverrides: 
*Exec <ProjectExec> will run on GPU
  *Expression <Alias> cast(dt#263L as string) AS dt#270 will run on GPU
    *Expression <Cast> cast(dt#263L as string) will run on GPU
  *Expression <Alias> from_unixtime(dt#263L, yyyyMMdd, Some(Etc/UTC)) AS from_unixtime(dt, yyyyMMdd)#271 will run on GPU
    *Expression <FromUnixTime> from_unixtime(dt#263L, yyyyMMdd, Some(Etc/UTC)) will run on GPU
  *Exec <ShuffleExchangeExec> will run on GPU
    *Partitioning <SinglePartition$> will run on GPU
    ! <LocalTableScanExec> cannot run on GPU because GPU does not currently support the operator class org.apache.spark.sql.execution.LocalTableScanExec
      @Expression <AttributeReference> dt#263L could run on GPU

+----------+---------------------------+
|        dt|from_unixtime(dt, yyyyMMdd)|
+----------+---------------------------+
|1701694288|                   20231204|
+----------+---------------------------+