feat(backoff): add initial delay support for backoff operations

[l1b0k]

• Introduce ExtendedBackoff struct to support initial delay
• Update backoff map to use ExtendedBackoff instead of wait.Backoff
• Modify ExponentialBackoffWithContext to include initial delay
• Update affected packages to use the new ExtendedBackoff structure
• Add tests for the new initial delay functionality

[codecov]

Codecov Report

❌ Patch coverage is 75.86207% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 35.66%. Comparing base (bff2c6b) to head (aa3ebe5).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/controller/eni/eni.go	35.71%	5 Missing and 4 partials ⚠️
pkg/backoff/backoff.go	86.95%	2 Missing and 1 partial ⚠️
pkg/controller/pod/pod_controller.go	50.00%	0 Missing and 1 partial ⚠️
pkg/eni/crdv2.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #860      +/-   ##
==========================================
+ Coverage   35.58%   35.66%   +0.07%     
==========================================
  Files         130      130              
  Lines       18890    18919      +29     
==========================================
+ Hits         6722     6747      +25     
  Misses      11413    11413              
- Partials      755      759       +4     

Flag	Coverage Δ
unittests	35.66% <75.86%> (+0.07%)	⬆️

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