chore: update golang dependencies, fix linting issues, and improve test coverage

[tekenstam]

Overview

This PR implements comprehensive updates to the codebase including Kubernetes dependency upgrades, linting fixes, and test coverage improvements. These changes align with modern Go practices and the Keikoproj development guidelines while maintaining backward compatibility.

Resolves #466

Key Changes

Dependency and Tooling Updates

• Updated Kubernetes dependencies to newer versions:
  • controller-runtime from v0.14.6 to v0.20.4
  • code-generator to v0.32.3
  • kube-openapi and related k8s.io packages
• Upgraded Go version to 1.24
• Updated controller-gen and golangci-lint tooling

Code Quality Improvements

• Fixed potential nil pointer dereferences through proper nil checks
• Added proper error handling for previously unchecked function calls
• Removed deprecated imports (replaced io/ioutil with os package)
• Eliminated unused variables and functions
• Improved loop efficiency with idiomatic Go patterns
• Standardized error handling patterns

CI/CD Enhancements

• Added golangci-lint to the push workflow
• Updated GitHub Actions and workflow configurations
• Enforced stricter linting rules in CI

Testing Improvements

• Added unit tests for controller reconcilers (spot events, nodes, configmaps, namespaces)
• Created tests for utility functions in common and kubernetes packages
• Improved test infrastructure for better reliability

Benefits

• More up-to-date and secure dependencies
• Better code quality and reliability through modern practices
• Reduced potential for runtime errors
• Better error handling and debugging capabilities
• Enforced linting in CI prevents regression
• Increased test coverage validates code behavior

Testing

• All unit tests are passing
• Linting now passes without warnings/errors
• Tested with updated Go 1.24 and dependencies
• Verified backward compatibility

This PR resolves #466 by addressing the identified linting issues while also modernizing the codebase through dependency updates and improved testing.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 37.50000% with 45 lines in your changes missing coverage. Please review.

Project coverage is 46.11%. Comparing base (a3d330a) to head (fb2234f).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
controllers/reconcilers.go	0.00%	25 Missing ⚠️
controllers/providers/aws/ec2.go	0.00%	4 Missing ⚠️
controllers/providers/aws/predicates.go	0.00%	4 Missing ⚠️
controllers/provisioners/eks/cloud.go	25.00%	2 Missing and 1 partial ⚠️
controllers/provisioners/eks/helpers.go	72.72%	2 Missing and 1 partial ⚠️
controllers/providers/kubernetes/utils.go	85.71%	2 Missing ⚠️
api/instancemgr/v1alpha1/instancegroup_types.go	66.66%	1 Missing ⚠️
controllers/common/utils.go	66.66%	1 Missing ⚠️
controllers/providers/aws/iam.go	0.00%	1 Missing ⚠️
...rollers/provisioners/eks/scaling/launchtemplate.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #467      +/-   ##
==========================================
+ Coverage   44.99%   46.11%   +1.12%     
==========================================
  Files          40       40              
  Lines        7017     7007      -10     
==========================================
+ Hits         3157     3231      +74     
+ Misses       3711     3620      -91     
- Partials      149      156       +7     

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[shaoxt]

LGTM