feat: get best block height from features API

[r4mmer]

Motivation

Get mining info API always returns height 0 on PoA side-dags and not the best chain height.

Acceptance Criteria

• Get best chain height from features API.

Security Checklist

• Make sure you do not include new dependencies in the project unless strictly necessary and do not include dev-dependencies as production ones. More dependencies increase the possibility of one of them being hijacked and affecting us.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.42%. Comparing base (6f3d6e9) to head (dd66396).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #541   +/-   ##
=======================================
  Coverage   90.42%   90.42%           
=======================================
  Files          56       56           
  Lines        2422     2423    +1     
  Branches      452      451    -1     
=======================================
+ Hits         2190     2191    +1     
  Misses        216      216           
  Partials       16       16           

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