broker bug fix: 1. send rewritten query to datanode 2. return empty hll result correctly 3. resultSize is not len(result)

[jshencode]

1. send rewritten query to data node which will rewrite enum string value to number
2. return empty hll result correctly
3. resultSize is not len(result)
4. rewritten dim not passed back

[codecov[bot]]

Codecov Report

Merging #308 into master will decrease coverage by 0.01%. The diff coverage is 81.48%.

@@            Coverage Diff             @@
##           master     #308      +/-   ##
==========================================
- Coverage   71.88%   71.86%   -0.02%     
==========================================
  Files         166      166              
  Lines       23252    23291      +39     
==========================================
+ Hits        16714    16739      +25     
- Misses       5246     5261      +15     
+ Partials     1292     1291       -1

Impacted Files	Coverage Δ
datanode/client/query_client.go	66.23% <0%> (-0.88%)	:arrow_down:
broker/query_plan_agg.go	81.18% <100%> (+1.32%)	:arrow_up:
broker/query_plan_non_agg.go	79.04% <100%> (+0.12%)	:arrow_up:
broker/query_compiler.go	59.23% <71.42%> (+0.54%)	:arrow_up:
controller/mutators/etcd/schema_mutator.go	61.84% <0%> (-1.74%)	:arrow_down:
subscriber/common/job/driver.go	66.31% <0%> (-1.42%)	:arrow_down:

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[voyager-dw]

lgtm