refactor(core-p2p): discover peers when checking network health

[spkjp]

Summary

A fork recovery's success depends on the number of available peers, so we should ensure enough peers are available.

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged

[codecov]

Codecov Report

Merging #3358 into develop will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #3358      +/-   ##
===========================================
+ Coverage    66.07%   66.07%   +<.01%     
===========================================
  Files          438      438              
  Lines        12263    12264       +1     
  Branches      1655     1655              
===========================================
+ Hits          8103     8104       +1     
  Misses        4127     4127              
  Partials        33       33

Impacted Files	Coverage Δ
packages/core-p2p/src/network-monitor.ts	73.35% <100%> (+0.1%)	⬆️

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