refactor: use WarnEventLogf

[lukasmetzner]

Additionally, adds unit tests for utils.WarnEventLogf.

[codecov]

Codecov Report

❌ Patch coverage is 77.77778% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.27%. Comparing base (b16f780) to head (6c37593).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/hcops/load_balancer.go	71.42%	4 Missing ⚠️
hcloud/instances.go	71.42%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1320      +/-   ##
==========================================
- Coverage   71.32%   71.27%   -0.05%     
==========================================
  Files          29       29              
  Lines        2877     2876       -1     
==========================================
- Hits         2052     2050       -2     
- Misses        634      635       +1     
  Partials      191      191              

Flag	Coverage Δ
e2e	44.63% <14.81%> (+0.05%)	⬆️
unit	67.73% <77.77%> (+0.09%)	⬆️

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