[SPARK-21566][SQL][PYTHON] Python method for summary
[SPARK-21566][SQL][PYTHON] Python method for summary

## What changes were proposed in this pull request?

Adds the recently added `summary` method to the python dataframe interface.

## How was this patch tested?

Additional inline doctests.

Author: Andrew Ray <ray.andrew@gmail.com>

Closes #18762 from aray/summary-py.

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