*: fix duties cache

[KaloyanTanev]

1. Previously we have tried to parse each proposer duty's key, but the proposer duty is the only duty request that don't filter on validator indices and rather returns all. In the previous implementation we had continue, what I've added now as well.
2. Add a bit more debug logging on reorg
3. Fix the cache metrics labels

category: bug
ticket: #4227

[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

[codecov]

Codecov Report

❌ Patch coverage is 18.18182% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.73%. Comparing base (33fe701) to head (3db315b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
app/eth2wrap/cache.go	20.00%	8 Missing ⚠️
core/validatorapi/validatorapi.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4263      +/-   ##
==========================================
+ Coverage   56.61%   56.73%   +0.11%     
==========================================
  Files         237      237              
  Lines       31329    31332       +3     
==========================================
+ Hits        17736    17775      +39     
+ Misses      11320    11285      -35     
+ Partials     2273     2272       -1     

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