Improve API errors

[Leo-Besancon]

• document all added functions
• try in sandbox /simulation/labnet
  • if part of node-launch, checked using the resync_check flag
• unit tests on the added/changed features
  • make tests compile
  • make tests pass
• add logs allowing easy debugging in case the changes caused problems
• if the API has changed, update the API specification

Notes:

• We kept the same behaviour as with send_operation, that if one request is invalid in the Vec of requests, then the whole call throws.

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 71.78%. Comparing base (df156f3) to head (2ca579c).

Files	Patch %	Lines
massa-api/src/public.rs	90.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4652   +/-   ##
=======================================
  Coverage   71.78%   71.78%           
=======================================
  Files         291      291           
  Lines       51642    51642           
=======================================
  Hits        37069    37069           
  Misses      14573    14573           

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