left-pad helm chart filenames with 0s to fix sorting

[laverya]

Description

Fixes # (issue)

Currently, helm chart apply order is determined by sorting the helm chart manifest filenames. The order is included as the first element in the filename, resulting in names like 1_helm_extension_chartname.yaml.

Manifests are fetched here, which uses filepath.Glob, which calls sort on the results.

Unfortunately, this breaks at 10 - 10_helm_extension_anothername.yaml is alphabetically before 1_helm_extension_chartname.yaml.

This PR adds a fmt directive to left-pad these integers to 9 digits, which allows sorting to work properly - see https://go.dev/play/p/THZg3TD6eHI.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation update

How Has This Been Tested?

• [ ] Manual test
• [ ] Auto test added

Checklist:

• [ ] My code follows the style guidelines of this project
• [x] My commit messages are signed-off
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [x] I have checked my code and corrected any misspellings