add istioctl ALS command for document

[lyzhang1999]

Related issues
#5060

[codecov]

Codecov Report

Merging #5066 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #5066      +/-   ##
============================================
+ Coverage     53.14%   53.16%   +0.01%     
- Complexity     2974     2975       +1     
============================================
  Files          1410     1410              
  Lines         30607    30607              
  Branches       3404     3404              
============================================
+ Hits          16267    16271       +4     
+ Misses        13538    13533       -5     
- Partials        802      803       +1     

Impacted Files	Coverage Δ	Complexity Δ
...er/storage/plugin/influxdb/query/MetricsQuery.java	50.83% <0.00%> (-0.84%)	10.00% <0.00%> (-1.00%)
...meter/function/AvgHistogramPercentileFunction.java	61.76% <0.00%> (-0.74%)	20.00% <0.00%> (-1.00%)
...r/storage/plugin/influxdb/query/MetadataQuery.java	60.00% <0.00%> (+0.76%)	12.00% <0.00%> (+1.00%)
...rary/client/elasticsearch/ElasticSearchClient.java	60.00% <0.00%> (+1.62%)	24.00% <0.00%> (ø%)
...earch7/query/ProfileThreadSnapshotQueryEs7DAO.java	100.00% <0.00%> (+50.00%)	3.00% <0.00%> (+2.00%)

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[hanahmily]

@lyzhang1999 Thanks for your contribution, most look good except for some nits.