Add a --set-time command that set's the node time using a provided timestamp or the host system clock

[ianmcorvidae]

Now that time isn't set by default and there's an admin message for this, we should be using it/allowing it. Bonus, this allows setting remote node time if I understand it correctly!

ref: meshtastic/firmware#4479

[codecov]

Codecov Report

Attention: Patch coverage is 21.42857% with 11 lines in your changes missing coverage. Please review.

Project coverage is 60.76%. Comparing base (de657ba) to head (40019a9).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
meshtastic/node.py	9.09%	10 Missing ⚠️
meshtastic/__main__.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #676      +/-   ##
==========================================
- Coverage   60.91%   60.76%   -0.15%     
==========================================
  Files          24       24              
  Lines        3689     3703      +14     
==========================================
+ Hits         2247     2250       +3     
- Misses       1442     1453      +11     

Flag	Coverage Δ
unittests	60.76% <21.42%> (-0.15%)	⬇️

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