[query] Add Graphite find integration test that verifies complex trees return valid results

[robskillington]

What this PR does / why we need it:

Previously we only had quite basic coverage of simple cases with the carbon docker integration tests for the find API (see https://github.com/m3db/m3/tree/v1.1.0/scripts/docker-integration-tests/carbon).

This adds a much more comprehensive and complex integration test that tests a complex tree and verifies all results in the tree are correctly returned when walking the tree and issuing queries.

Special notes for your reviewer:

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]

Codecov Report

Merging #3636 (29722e7) into master (ddcfc1f) will decrease coverage by 1.0%.
The diff coverage is n/a.

❗ Current head 29722e7 differs from pull request most recent head d55db2c. Consider uploading reports for the commit d55db2c to get more accurate results

@@           Coverage Diff            @@
##           master   #3636     +/-   ##
========================================
- Coverage    57.3%   56.3%   -1.1%     
========================================
  Files         551     551             
  Lines       62978   61868   -1110     
========================================
- Hits        36137   34872   -1265     
- Misses      23648   23879    +231     
+ Partials     3193    3117     -76     

Flag	Coverage Δ
aggregator	57.1% <0.0%> (-5.6%)	⬇️
cluster	∅ <0.0%> (∅)
collector	58.4% <0.0%> (?)
dbnode	60.9% <0.0%> (-0.5%)	⬇️
m3em	46.4% <0.0%> (ø)
metrics	19.8% <0.0%> (+0.1%)	⬆️
msg	74.5% <0.0%> (-0.2%)	⬇️

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[linasm]

LGTM, with #3639 being one possible way to make the test green.