Improve GitHub Action Workflows and Fix Linting Issues

[tekenstam]

Summary

This PR makes two key improvements to the instance-manager project:

1. Restructures GitHub Actions workflows for better organization and efficiency
2. Fixes various code quality issues identified by golangci-lint

GitHub Actions Improvements

Workflow Separation

• ✅ Extracted CodeQL analysis into a dedicated workflow file
• ✅ Extracted Golangci-lint checks into a dedicated workflow file
• ✅ Removed redundant steps from existing workflows to avoid duplication

Docker Build/Push Improvements

• ✅ Added proper semantic version tagging with docker/metadata-action
• ✅ Enhanced multi-architecture build support
• ✅ Improved conditional image pushing (skip on PRs)
• ✅ Added proper GitHub permissions for workflow operations

Code Quality Fixes

• ✅ Fixed embedded field issues:
  • Removed direct .ObjectMeta references for better structure
  • Used proper pattern for DeletionTimestamp access
• ✅ Improved code structure in AWS worker:
  • Lifted counter condition into loop condition
  • Used tagged switch instead of if-else chains
• ✅ Fixed error return order in functions to follow Go conventions
• ✅ Corrected error message capitalization to follow Go best practices
• ✅ Updated corresponding tests to match corrected error formats

Testing

All unit tests are passing with the changes.

Compatibility

These changes maintain full backward compatibility with existing functionality.

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 60.52632% with 15 lines in your changes missing coverage. Please review.

Project coverage is 46.13%. Comparing base (bce2d0c) to head (62270ac).

Files with missing lines	Patch %	Lines
controllers/instancegroup_controller.go	0.00%	6 Missing ⚠️
controllers/providers/aws/aws.go	0.00%	5 Missing ⚠️
controllers/providers/aws/eks.go	0.00%	3 Missing ⚠️
controllers/provisioners/eks/helpers.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #470      +/-   ##
==========================================
+ Coverage   46.11%   46.13%   +0.01%     
==========================================
  Files          40       40              
  Lines        7007     7004       -3     
==========================================
  Hits         3231     3231              
+ Misses       3620     3617       -3     
  Partials      156      156              

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