Add NodeId::from_slice

[benthecarman]

nice utility function

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 89.18%. Comparing base (36e434d) to head (227d73d).
Report is 64 commits behind head on main.

Files	Patch %	Lines
lightning/src/routing/gossip.rs	0.00%	8 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2942      +/-   ##
==========================================
+ Coverage   89.13%   89.18%   +0.05%     
==========================================
  Files         117      117              
  Lines       94657    95530     +873     
  Branches    94657    95530     +873     
==========================================
+ Hits        84369    85202     +833     
- Misses       7811     7844      +33     
- Partials     2477     2484       +7     

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[tnull]

Thanks!

Simple enough, so I'll just go ahead and merge this.