[coordinator] add support for tags in rollup rules

[shreyassrivatsan]

What this PR does / why we need it: This PR adds support for custom tags in rollup rule definitions. These tags will enable different functionality in rollup rules based on provided custom tags.

Does this PR introduce a user-facing and/or backwards incompatible change?: NONE

Does this PR require updating code package or user-facing documentation?: NONE

[codecov[bot]]

Codecov Report

Merging #3279 (1094af8) into master (812d585) will decrease coverage by 20.6%. Report is 695 commits behind head on master. The diff coverage is 40.9%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3279      +/-   ##
==========================================
- Coverage    71.1%    50.5%   -20.6%     
==========================================
  Files        1098     1089       -9     
  Lines      101644   100355    -1289     
==========================================
- Hits        72291    50749   -21542     
- Misses      24245    45374   +21129     
+ Partials     5108     4232     -876     

Flag	Coverage Δ
aggregator	60.2% <ø> (-16.3%)	:arrow_down:
cluster	48.1% <ø> (-36.7%)	:arrow_down:
collector	54.3% <ø> (-30.0%)	:arrow_down:
dbnode	70.0% <ø> (-5.7%)	:arrow_down:
m3em	52.2% <ø> (-22.2%)	:arrow_down:
m3ninx	60.3% <ø> (-13.3%)	:arrow_down:
metrics	20.0% <40.9%> (+<0.1%)	:arrow_up:
msg	73.9% <ø> (-0.2%)	:arrow_down:
query	13.5% <ø> (-53.8%)	:arrow_down:
x	54.0% <ø> (-26.6%)	:arrow_down:

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