[MINOR][DOC] Add "completedStages" metircs for namespace=appStatus
[MINOR][DOC] Add "completedStages" metircs for namespace=appStatus

## What changes were proposed in this pull request?

Add completedStages metircs for  namespace=appStatus for monitoring.md.

Closes #24109 from hehuiyuan/hehuiyuan-patch-5.

Authored-by: hehuiyuan <69a1bf9d3b307854d4995a83e3150ff6d24770d1@ZBMAC-C02WD3K5H.local>
Signed-off-by: Sean Owen <3f9d48d7c3f24f7009479c5fa630bd1131ffc724@databricks.com>

holdenk/spark,holdenk/spark,milliman/spark,ConeyLiu/spark,wzhfy/spark,chuckchen/spark,witgo/spark,witgo/spark,pgandhi999/spark,shaneknapp/spark,shuangshuangwang/spark,zero323/spark,jiangxb1987/spark,chuckchen/spark,bdrillard/spark,Aegeaner/spark,chuckchen/spark,vinodkc/spark,zuotingbing/spark,Aegeaner/spark,caneGuy/spark,wzhfy/spark,shuangshuangwang/spark,jiangxb1987/spark,matthewfranglen/spark,darionyaphet/spark,zzcclp/spark,kiszk/spark,icexelloss/spark,HyukjinKwon/spark,shaneknapp/spark,kevinyu98/spark,dbtsai/spark,taroplus/spark,ueshin/apache-spark,rezasafi/spark,xuanyuanking/spark,pgandhi999/spark,kiszk/spark,chuckchen/spark,mahak/spark,BryanCutler/spark,WeichenXu123/spark,actuaryzhang/spark,chuckchen/spark,skonto/spark,Aegeaner/spark,jiangxb1987/spark,chuckchen/spark,BryanCutler/spark,caneGuy/spark,milliman/spark,wangyum/spark,skonto/spark,wangyum/spark,pgandhi999/spark,JoshRosen/spark,rednaxelafx/apache-spark,spark-test/spark,bdrillard/spark,cloud-fan/spark,kiszk/spark,Aegeaner/spark,bdrillard/spark,highfei2011/spark,darionyaphet/spark,highfei2011/spark,kevinyu98/spark,zzcclp/spark,dbtsai/spark,hvanhovell/spark,gengliangwang/spark,zzcclp/spark,rezasafi/spark,shaneknapp/spark,dongjoon-hyun/spark,nchammas/spark,nchammas/spark,bdrillard/spark,wangmiao1981/spark,LantaoJin/spark,darionyaphet/spark,hvanhovell/spark,actuaryzhang/spark,wzhfy/spark,maropu/spark,nchammas/spark,JoshRosen/spark,JoshRosen/spark,vinodkc/spark,rednaxelafx/apache-spark,ConeyLiu/spark,vinodkc/spark,actuaryzhang/spark,caneGuy/spark,Aegeaner/spark,skonto/spark,mahak/spark,icexelloss/spark,highfei2011/spark,shuangshuangwang/spark,kiszk/spark,kiszk/spark,srowen/spark,taroplus/spark,highfei2011/spark,wangmiao1981/spark,dongjoon-hyun/spark,dbtsai/spark,milliman/spark,caneGuy/spark,zzcclp/spark,vinodkc/spark,witgo/spark,apache/spark,apache/spark,ptkool/spark,kevinyu98/spark,goldmedal/spark,holdenk/spark,zero323/spark,jiangxb1987/spark,kevinyu98/spark,dongjoon-hyun/spark,cloud-fan/spark,wzhfy/spark,ConeyLiu/spark,mahak/spark,mahak/spark,vinodkc/spark,goldmedal/spark,hvanhovell/spark,rednaxelafx/apache-spark,aosagie/spark,aosagie/spark,wangyum/spark,xuanyuanking/spark,holdenk/spark,maropu/spark,dbtsai/spark,srowen/spark,ueshin/apache-spark,zuotingbing/spark,gengliangwang/spark,aosagie/spark,witgo/spark,goldmedal/spark,srowen/spark,xuanyuanking/spark,apache/spark,gengliangwang/spark,kevinyu98/spark,gengliangwang/spark,techaddict/spark,dongjoon-hyun/spark,wangmiao1981/spark,darionyaphet/spark,Aegeaner/spark,maropu/spark,jkbradley/spark,HyukjinKwon/spark,xuanyuanking/spark,aosagie/spark,LantaoJin/spark,taroplus/spark,holdenk/spark,LantaoJin/spark,shaneknapp/spark,actuaryzhang/spark,rezasafi/spark,techaddict/spark,xuanyuanking/spark,jiangxb1987/spark,maropu/spark,hvanhovell/spark,HyukjinKwon/spark,dongjoon-hyun/spark,WeichenXu123/spark,zzcclp/spark,aosagie/spark,BryanCutler/spark,ConeyLiu/spark,zero323/spark,jkbradley/spark,techaddict/spark,ptkool/spark,kiszk/spark,srowen/spark,bdrillard/spark,kevinyu98/spark,HyukjinKwon/spark,spark-test/spark,holdenk/spark,dongjoon-hyun/spark,rednaxelafx/apache-spark,xuanyuanking/spark,cloud-fan/spark,vinodkc/spark,nchammas/spark,srowen/spark,apache/spark,HyukjinKwon/spark,taroplus/spark,highfei2011/spark,dbtsai/spark,LantaoJin/spark,BryanCutler/spark,caneGuy/spark,darionyaphet/spark,cloud-fan/spark,ptkool/spark,hvanhovell/spark,jkbradley/spark,apache/spark,zero323/spark,jkbradley/spark,holdenk/spark,highfei2011/spark,HyukjinKwon/spark,zuotingbing/spark,nchammas/spark,icexelloss/spark,zuotingbing/spark,witgo/spark,ueshin/apache-spark,taroplus/spark,pgandhi999/spark,actuaryzhang/spark,rezasafi/spark,nchammas/spark,goldmedal/spark,gengliangwang/spark,rednaxelafx/apache-spark,mahak/spark,pgandhi999/spark,mahak/spark,JoshRosen/spark,shaneknapp/spark,apache/spark,taroplus/spark,shaneknapp/spark,BryanCutler/spark,LantaoJin/spark,LantaoJin/spark,milliman/spark,milliman/spark,gengliangwang/spark,cloud-fan/spark,ConeyLiu/spark,ptkool/spark,nchammas/spark,wangmiao1981/spark,HyukjinKwon/spark,rezasafi/spark,dbtsai/spark,techaddict/spark,skonto/spark,shaneknapp/spark,kevinyu98/spark,wangyum/spark,ptkool/spark,jiangxb1987/spark,LantaoJin/spark,wangyum/spark,techaddict/spark,bdrillard/spark,WeichenXu123/spark,pgandhi999/spark,zero323/spark,zzcclp/spark,srowen/spark,mahak/spark,milliman/spark,xuanyuanking/spark,WeichenXu123/spark,shuangshuangwang/spark,caneGuy/spark,dongjoon-hyun/spark,caneGuy/spark,maropu/spark,jkbradley/spark,ueshin/apache-spark,skonto/spark,Aegeaner/spark,gengliangwang/spark,dbtsai/spark,ConeyLiu/spark,techaddict/spark,zuotingbing/spark,skonto/spark,JoshRosen/spark,jiangxb1987/spark,wangmiao1981/spark,chuckchen/spark,skonto/spark,witgo/spark,wzhfy/spark,apache/spark,milliman/spark,wangmiao1981/spark,rednaxelafx/apache-spark,BryanCutler/spark,ueshin/apache-spark,maropu/spark,zzcclp/spark,aosagie/spark,maropu/spark,BryanCutler/spark,pgandhi999/spark,icexelloss/spark,rezasafi/spark,aosagie/spark,zuotingbing/spa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