feat(onboarding): Add rpc endpoint juno_getNodesFromRoot

[hudem1]

Onboarding implementation task 2: endpoint juno_getNodesFromRoot

I set it as draft just to make sure it doesn't get merged.

[codecov]

Codecov Report

Attention: Patch coverage is 65.38462% with 9 lines in your changes missing coverage. Please review.

Project coverage is 74.33%. Comparing base (198443f) to head (83bda67).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
rpc/block.go	47.05%	6 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2432      +/-   ##
==========================================
- Coverage   74.42%   74.33%   -0.10%     
==========================================
  Files         113      113              
  Lines       13135    13155      +20     
==========================================
+ Hits         9776     9779       +3     
- Misses       2619     2640      +21     
+ Partials      740      736       -4     

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[rodrigo-pino]

LGTM! Closing