cmd/createcluster: fix pre-gen builder registrations

[dB2510]

This PR fixes a bug in the create cluster command that was generating incorrect builder registrations in cluster-lock.json. The issue stemmed from the usage of withdrawal addresses instead of fee recipient addresses, which resulted in signature verification failures when the command was used for the 'charon run' operation.

Here's the error log caused by this bug:

category: bug
ticket: #2674

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e4f2047) 53.00% compared to head (e66bb4c) 53.03%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2673      +/-   ##
==========================================
+ Coverage   53.00%   53.03%   +0.03%     
==========================================
  Files         202      202              
  Lines       28006    28006              
==========================================
+ Hits        14844    14853       +9     
+ Misses      11301    11292       -9     
  Partials     1861     1861              

Files	Coverage Δ
cmd/createcluster.go	59.82% <100.00%> (ø)

... and 8 files with indirect coverage changes

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[OisinKyne]

Small feedback @dB2510

This PR fixes a critical bug in the create cluster command

I think we should develop a shared framework for how we name bug severities. This would have made mev registrations fail for a specific subset of scenarios, and local block production may have worked. Either way, I would not put 'could miss block' in the critical category here, and would save that for loss of funds not missed opportunities.

[dB2510]

Hey @OisinKyne
Yeah agreed, this is not a critical bug which can cause loss of funds. This bug was not letting charon to start as it was failing initial cluster-lock verification which is why I mentioned it as a critical bug. It can be mitigated with the --no-verify flag and then everything will work as expected even the block proposals.
Updated the PR description 👍