ncu-ci: create INFRA_FAILURES category

[mmarchini]

Some errors we see are caused by underlying infrastructure issues (most
commonly filesystem corruption). Correctly classifying can help when
collecting statistics, when pinging the build team, or even for
automated notification (see
nodejs/build#2359).

[codecov]

Codecov Report

Merging #441 into master will increase coverage by 1.09%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##           master     #441      +/-   ##
==========================================
+ Coverage   75.98%   77.08%   +1.09%     
==========================================
  Files          21       21              
  Lines        1445     1501      +56     
==========================================
+ Hits         1098     1157      +59     
+ Misses        347      344       -3     

Impacted Files	Coverage Δ
lib/ci/ci_failure_parser.js	79.16% <60.00%> (+1.14%)	⬆️
lib/pr_checker.js	95.49% <0.00%> (-1.99%)	⬇️
lib/file.js	78.26% <0.00%> (-0.91%)	⬇️
lib/ci/ci_type_parser.js	81.25% <0.00%> (+0.29%)	⬆️
lib/cli.js	90.00% <0.00%> (+0.76%)	⬆️
lib/ci/ci_result_parser.js	47.87% <0.00%> (+1.81%)	⬆️

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