return JSON from hare weight, total weight and beacon APIs

[poszu]

First part of #6623. Refactors:

• /hare/total_weight/{layer}
• /hare/weight/{node_id}/{layer}
• /hare/beacon/{epoch}

[codecov]

Codecov Report

Attention: Patch coverage is 72.22222% with 20 lines in your changes missing coverage. Please review.

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Report is 2 commits behind head on node-split-poc.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
api/node/client/client.gen.go	68.5%	8 Missing and 3 partials ⚠️
api/node/client/client.go	57.1%	9 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##             node-split-poc   #6627   +/-   ##
================================================
  Coverage                  ?   77.7%           
================================================
  Files                     ?     376           
  Lines                     ?   51419           
  Branches                  ?       0           
================================================
  Hits                      ?   39992           
  Misses                    ?    9052           
  Partials                  ?    2375           

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