Add STUN support for connections

[soffokl]

No description provided.

[codecov-commenter]

Codecov Report

Merging #3376 (0a529dd) into master (a612f51) will decrease coverage by 0.00%.
The diff coverage is 55.69%.

@@            Coverage Diff             @@
##           master    #3376      +/-   ##
==========================================
- Coverage   43.56%   43.56%   -0.01%     
==========================================
  Files         319      320       +1     
  Lines       14048    14122      +74     
==========================================
+ Hits         6120     6152      +32     
- Misses       7204     7237      +33     
- Partials      724      733       +9     

Impacted Files	Coverage Δ
p2p/common.go	56.52% <ø> (ø)
p2p/contact.go	0.00% <ø> (ø)
p2p/dialer.go	58.27% <0.00%> (ø)
p2p/stun.go	53.42% <53.42%> (ø)
p2p/listener.go	63.05% <100.00%> (+0.18%)	⬆️
core/policy/oracle.go	83.87% <0.00%> (-6.46%)	⬇️
core/discovery/brokerdiscovery/repository.go	76.36% <0.00%> (-5.46%)	⬇️
requests/dialer_swarm.go	76.34% <0.00%> (-3.23%)	⬇️
nat/traversal/pinger.go	74.03% <0.00%> (+1.10%)	⬆️

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