handle phase 5 non-status evidence in drug collapse

[afaulconbridge]

As described opentargets/issues#682 (comment) the drug evidence collapse was inadvertently omitting evidence with phase V and without a status.

I've re-structured the Elasticsearch JSON query to allow for this, using a series of nested aggregations instead of a composite one.

[codecov]

Codecov Report

Merging #200 into master will decrease coverage by 0.15%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #200      +/-   ##
==========================================
- Coverage   19.39%   19.23%   -0.16%     
==========================================
  Files          33       33              
  Lines        3089     3114      +25     
==========================================
  Hits          599      599              
- Misses       2490     2515      +25

Impacted Files	Coverage Δ
app/common/elasticsearchclient.py	14.6% <0%> (-0.25%)	⬇️

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