Get health from composite indicators

[OlgaMaciaszek]

Fixes gh-4072.

[codecov]

Codecov Report

Merging #4074 (c0b709a) into 3.1.x (c350c88) will increase coverage by 0.57%.
The diff coverage is 90.00%.

@@             Coverage Diff              @@
##              3.1.x    #4074      +/-   ##
============================================
+ Coverage     55.26%   55.83%   +0.57%     
- Complexity      511      521      +10     
============================================
  Files            57       57              
  Lines          2470     2477       +7     
  Branches        226      231       +5     
============================================
+ Hits           1365     1383      +18     
+ Misses         1019     1006      -13     
- Partials         86       88       +2     

Impacted Files	Coverage Δ
...cloud/netflix/eureka/EurekaHealthCheckHandler.java	91.04% <90.00%> (+12.71%)	⬆️
...rk/cloud/netflix/eureka/EurekaDiscoveryClient.java	34.78% <0.00%> (+17.39%)	⬆️

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[spencergibb]

New tests?

[OlgaMaciaszek]

Merging since all the review suggestions have been addressed.