[SPARK-36377][DOCS] Re-document "Options read in YARN client/cluster mode" section in spark-env.sh.template
[SPARK-36377][DOCS] Re-document "Options read in YARN client/cluster mode" section in spark-env.sh.template

### What changes were proposed in this pull request?

Edit spark-env.sh.template for better documentation.

### Why are the changes needed?

Some options  (e.g. SPARK_CONF_DIR, SPARK_EXECUTOR_CORES, etc.) are read by any mode but are in the "Options read in YARN client/cluster mode" that might confuse users, so we should separate YARN only options from others.

### Does this PR introduce _any_ user-facing change?

Yes, docs changed.

### How was this patch tested?

Just a manual checking.
<img width="336" alt="options" src="https://user-images.githubusercontent.com/87687356/127804872-02a27337-f304-47df-affa-a8c4e9e98fe5.png">

Closes #33604 from yutoacts/SPARK-36377.

Authored-by: Yuto Akutsu <1c5eb9c01483db9a7c7ede8ddfc9fb2c3578ed75@nttdata.com>
Signed-off-by: Hyukjin Kwon <2680965ad5aae29275c8fb10150cb10f5554e78b@apache.org>

jiangxb1987/spark,srowen/spark,taroplus/spark,chuckchen/spark,cloud-fan/spark,apache/spark,gengliangwang/spark,chuckchen/spark,shaneknapp/spark,HyukjinKwon/spark,rednaxelafx/apache-spark,cloud-fan/spark,JoshRosen/spark,hvanhovell/spark,rednaxelafx/apache-spark,dongjoon-hyun/spark,WeichenXu123/spark,srowen/spark,witgo/spark,witgo/spark,vinodkc/spark,wangyum/spark,xuanyuanking/spark,xuanyuanking/spark,taroplus/spark,nchammas/spark,holdenk/spark,xuanyuanking/spark,mahak/spark,ueshin/apache-spark,holdenk/spark,zzcclp/spark,apache/spark,HyukjinKwon/spark,nchammas/spark,dongjoon-hyun/spark,zzcclp/spark,zzcclp/spark,jiangxb1987/spark,apache/spark,gengliangwang/spark,dongjoon-hyun/spark,taroplus/spark,dongjoon-hyun/spark,hvanhovell/spark,WeichenXu123/spark,wangyum/spark,zzcclp/spark,wangyum/spark,vinodkc/spark,vinodkc/spark,xuanyuanking/spark,zzcclp/spark,zero323/spark,zero323/spark,mahak/spark,jiangxb1987/spark,hvanhovell/spark,ueshin/apache-spark,xuanyuanking/spark,mahak/spark,apache/spark,shaneknapp/spark,rednaxelafx/apache-spark,zero323/spark,jiangxb1987/spark,gengliangwang/spark,chuckchen/spark,holdenk/spark,nchammas/spark,gengliangwang/spark,apache/spark,wangyum/spark,HyukjinKwon/spark,ueshin/apache-spark,HyukjinKwon/spark,HyukjinKwon/spark,dongjoon-hyun/spark,HyukjinKwon/spark,cloud-fan/spark,jiangxb1987/spark,nchammas/spark,cloud-fan/spark,zero323/spark,nchammas/spark,jiangxb1987/spark,shaneknapp/spark,wangyum/spark,rednaxelafx/apache-spark,rednaxelafx/apache-spark,JoshRosen/spark,taroplus/spark,zero323/spark,chuckchen/spark,holdenk/spark,zzcclp/spark,JoshRosen/spark,ueshin/apache-spark,rednaxelafx/apache-spark,vinodkc/spark,jiangxb1987/spark,WeichenXu123/spark,xuanyuanking/spark,witgo/spark,dongjoon-hyun/spark,zzcclp/spark,hvanhovell/spark,JoshRosen/spark,witgo/spark,chuckchen/spark,dongjoon-hyun/spark,shaneknapp/spark,WeichenXu123/spark,WeichenXu123/spark,srowen/spark,HyukjinKwon/spark,rednaxelafx/apache-spark,cloud-fan/spark,JoshRosen/spark,srowen/spark,holdenk/spark,mahak/spark,WeichenXu123/spark,vinodkc/spark,witgo/spark,wangyum/spark,apache/spark,taroplus/spark,xuanyuanking/spark,ueshin/apache-spark,ueshin/apache-spark,shaneknapp/spark,mahak/spark,chuckchen/spark,shaneknapp/spark,hvanhovell/spark,taroplus/spark,JoshRosen/spark,zero323/spark,mahak/spark,witgo/spark,chuckchen/spark,WeichenXu123/spark,holdenk/spark,gengliangwang/spark,witgo/spark,gengliangwang/spark,cloud-fan/spark,vinodkc/spark,vinodkc/spark,taroplus/spark,srowen/spark,hvanhovell/spark,mahak/spark,zero323/spark,nchammas/spark,apache/spark,gengliangwang/spark,wangyum/spark,ueshin/apache-spark,hvanhovell/spark,srowen/spark,srowen/spark,holdenk/spark,cloud-fan/spark,nchammas/spark,JoshRosen/spark,shaneknapp/spark