Export ssh public keys under ssh-pub-keys in topo json

[hellt]

For external systems acting on containerlab topologies and creating automations around the nodes spawned with Containerlab it is beneficial to export the SSH public keys that containerlab extracted during its run.

This will enable tools to read the topology json and potentially add those keys at the post-deploy stage using automation tools available to a user

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.88%. Comparing base (dd321ab) to head (02bf3cc).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2387      +/-   ##
==========================================
- Coverage   51.91%   51.88%   -0.03%     
==========================================
  Files         173      172       -1     
  Lines       17299    17302       +3     
==========================================
- Hits         8980     8978       -2     
- Misses       7378     7381       +3     
- Partials      941      943       +2     

Files with missing lines	Coverage Δ
clab/export.go	75.32% <100.00%> (+5.58%)	⬆️
nodes/srl/version.go	75.43% <100.00%> (ø)
utils/ssh.go	91.66% <100.00%> (+8.33%)	⬆️

... and 2 files with indirect coverage changes

[FloSch62]

Cool, I can use that for the clab connector too

[hellt]

yup, I did it for the NodeUser generation specifically