[SPARK-20736][PYTHON] PySpark StringIndexer supports StringOrderType
[SPARK-20736][PYTHON] PySpark StringIndexer supports StringOrderType

## What changes were proposed in this pull request?
PySpark StringIndexer supports StringOrderType added in #17879.

Author: Wayne Zhang <actuaryzhang@uber.com>

Closes #17978 from actuaryzhang/PythonStringIndexer.

1haodian/spark,zero323/spark,lvdongr/spark,bOOm-X/spark,kiszk/spark,UndeadBaneGitHub/spark,michalsenkyr/spark,michalsenkyr/spark,narahari92/spark,michalsenkyr/spark,liutang123/spark,cloud-fan/spark,techaddict/spark,sureshthalamati/spark,someorz/spark,WindCanDie/spark,liyichao/spark,aokolnychyi/spark,nchammas/spark,maropu/spark,brad-kaiser/spark,szhem/spark,huang1900/spark,HyukjinKwon/spark,wzhfy/spark,narahari92/spark,aray/spark,rednaxelafx/apache-spark,minixalpha/spark,actuaryzhang/spark,setjet/spark,sureshthalamati/spark,nlalevee/spark,goldmedal/spark,chuckchen/spark,ioana-delaney/spark,kiszk/spark,apache/spark,yanboliang/spark,zero323/spark,HyukjinKwon/spark,minixalpha/spark,aosagie/spark,saltstar/spark,nchammas/spark,map222/spark,guoxiaolongzte/spark,ConeyLiu/spark,alunarbeach/spark,poffuomo/spark,saltstar/spark,WeichenXu123/spark,nilsgrabbert/spark,kevinyu98/spark,LantaoJin/spark,vinodkc/spark,highfei2011/spark,maropu/spark,ConeyLiu/spark,bravo-zhang/spark,WeichenXu123/spark,alunarbeach/spark,liutang123/spark,poffuomo/spark,shaneknapp/spark,ericvandenbergfb/spark,panfengfeng/spark,rekhajoshm/spark,ptkool/spark,saturday-shi/spark,shaneknapp/spark,LantaoJin/spark,nchammas/spark,apache/spark,milliman/spark,hhbyyh/spark,UndeadBaneGitHub/spark,guoxiaolongzte/spark,dongjoon-hyun/spark,stanzhai/spark,gengliangwang/spark,aosagie/spark,stanzhai/spark,setjet/spark,wzhfy/spark,aray/spark,vinodkc/spark,ahnqirage/spark,shaneknapp/spark,rednaxelafx/apache-spark,gengliangwang/spark,szhem/spark,rekhajoshm/spark,michalsenkyr/spark,mahak/spark,shuangshuangwang/spark,cin/spark,ioana-delaney/spark,sureshthalamati/spark,guoxiaolongzte/spark,adrian-ionescu/apache-spark,taroplus/spark,tejasapatil/spark,debugger87/spark,esi-mineset/spark,dongjoon-hyun/spark,nlalevee/spark,tejasapatil/spark,akopich/spark,1haodian/spark,JoshRosen/spark,kiszk/spark,cloud-fan/spark,bOOm-X/spark,darionyaphet/spark,hvanhovell/spark,taroplus/spark,highfei2011/spark,xflin/spark,bdrillard/spark,UndeadBaneGitHub/spark,eyalfa/spark,ioana-delaney/spark,hvanhovell/spark,pgandhi999/spark,kevinyu98/spark,UndeadBaneGitHub/spark,SHASHANKB/spark,rikima/spark,bOOm-X/spark,nlalevee/spark,brad-kaiser/spark,milliman/spark,ConeyLiu/spark,ajaysaini725/spark,lxsmnv/spark,1haodian/spark,byakuinss/spark,stanzhai/spark,brad-kaiser/spark,stanzhai/spark,byakuinss/spark,xuanyuanking/spark,ptkool/spark,jiangxb1987/spark,srowen/spark,guoxiaolongzte/spark,ptkool/spark,markhamstra/spark,esi-mineset/spark,actuaryzhang/spark,bdrillard/spark,darionyaphet/spark,zero323/spark,LantaoJin/spark,setjet/spark,nilsgrabbert/spark,actuaryzhang/spark,yanboliang/spark,sahilTakiar/spark,icexelloss/spark,taroplus/spark,shubhamchopra/spark,cloud-fan/spark,markhamstra/spark,dhruve/spark,goldmedal/spark,1haodian/spark,zzcclp/spark,saltstar/spark,esi-mineset/spark,spark-test/spark,holdenk/spark,nilsgrabbert/spark,kiszk/spark,wzhfy/spark,minixalpha/spark,apache/spark,markhamstra/spark,WindCanDie/spark,maropu/spark,alunarbeach/spark,jkbradley/spark,ahnqirage/spark,rednaxelafx/apache-spark,zzcclp/spark,rezasafi/spark,bdrillard/spark,kissmetrics/spark,esi-mineset/spark,wangmiao1981/spark,tejasapatil/spark,panfengfeng/spark,nlalevee/spark,cloud-fan/spark,BryanCutler/spark,caneGuy/spark,mahak/spark,tejasapatil/spark,goldmedal/spark,rikima/spark,UndeadBaneGitHub/spark,ericvandenbergfb/spark,mike0sv/spark,jkbradley/spark,dongjoon-hyun/spark,BryanCutler/spark,SHASHANKB/spark,highfei2011/spark,cin/spark,tejasapatil/spark,liyichao/spark,saturday-shi/spark,sahilTakiar/spark,byakuinss/spark,debugger87/spark,aray/spark,janewangfb/spark,someorz/spark,caneGuy/spark,joseph-torres/spark,tengpeng/spark,highfei2011/spark,aosagie/spark,alunarbeach/spark,liutang123/spark,jkbradley/spark,holdenk/spark,hvanhovell/spark,huang1900/spark,SHASHANKB/spark,bdrillard/spark,saltstar/spark,map222/spark,saltstar/spark,kissmetrics/spark,ueshin/apache-spark,ioana-delaney/spark,jiangxb1987/spark,zuotingbing/spark,ddna1021/spark,WeichenXu123/spark,techaddict/spark,mdespriee/spark,eyalfa/spark,dhruve/spark,hvanhovell/spark,jkbradley/spark,alunarbeach/spark,cloud-fan/spark,facaiy/spark,aokolnychyi/spark,eyalfa/spark,ron8hu/spark,brad-kaiser/spark,jkbradley/spark,saltstar/spark,bOOm-X/spark,mdespriee/spark,nilsgrabbert/spark,esi-mineset/spark,cloud-fan/spark,joseph-torres/spark,mzl9039/spark,zhouyejoe/spark,sahilTakiar/spark,witgo/spark,alunarbeach/spark,andrewor14/spark,rezasafi/spark,markhamstra/spark,rednaxelafx/apache-spark,cloud-fan/spark,rezasafi/spark,zero323/spark,panfengfeng/spark,poffuomo/spark,michalsenkyr/spark,zero323/spark,dbtsai/spark,liyichao/spark,eyalfa/spark,brad-kaiser/spark,aokolnychyi/spark,rednaxelafx/apache-spark,bdrillard/spark,mike0sv/spark,WeichenXu123/spark,skonto/spark,jiangxb1987/spark,ron8hu/spark,vinodkc/spark,mzl9039/spark,maropu/spark,ericvandenbergfb/spark,michalsenkyr/spark,tengpeng/spark,adrian-ionescu/apache-spark,ptkool/spark,holdenk/spark,shubhamchopra/spark,zzcclp/spark,LantaoJin/spark,kiszk/spark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