app: add beacon node peer_id metric

[DiogoSantoss]

Add new metric app_beacon_node_peer_id to track beacon node's peer IDs.

category: feature
ticket: #4197

[codecov]

Codecov Report

❌ Patch coverage is 0% with 26 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.60%. Comparing base (f9042d5) to head (6435f07).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
app/eth2wrap/multi.go	0.00%	11 Missing ⚠️
app/monitoringapi.go	0.00%	10 Missing ⚠️
app/eth2wrap/lazy.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4256      +/-   ##
==========================================
- Coverage   56.91%   56.60%   -0.31%     
==========================================
  Files         237      237              
  Lines       31004    31332     +328     
==========================================
+ Hits        17646    17737      +91     
- Misses      11108    11322     +214     
- Partials     2250     2273      +23     

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud