Remove wrapper types for get header response

[avalonche]

📝 Summary

Previously wrapper types were made to process both bellatrix types from go-boost-utils and attestant types which includes capella types. As part of #529 this removes wrapper types as the bellatrix types from go-boost-utils will no longer be needed.

⛱ Motivation and Context

📚 References

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✅ I have run these commands

• make lint
• make test-race
• go mod tidy

[codecov-commenter]

Codecov Report

Merging #538 (2720a38) into remove-process-bellatrix-payload (9a16491) will decrease coverage by 0.87%.
The diff coverage is 64.81%.

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@@                         Coverage Diff                          @@
##           remove-process-bellatrix-payload     #538      +/-   ##
====================================================================
- Coverage                             71.11%   70.24%   -0.87%     
====================================================================
  Files                                     8        7       -1     
  Lines                                  1177     1099      -78     
====================================================================
- Hits                                    837      772      -65     
+ Misses                                  305      283      -22     
- Partials                                 35       44       +9     

Flag	Coverage Δ
unittests	70.24% <64.81%> (-0.87%)	⬇️

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Impacted Files	Coverage Δ
server/utils.go	75.00% <44.89%> (-7.59%)	⬇️
server/service.go	80.41% <71.05%> (-2.04%)	⬇️
server/mock_relay.go	92.18% <100.00%> (+1.88%)	⬆️

[metachris]

please rebase