fix: de-duplicate same dpkg packages with different filePaths from different layers

[DmitriyLewen]

Description

See #8297

Related issues

• Close fix(dpkg): de-duplicate same packages with different filePaths from different layers #8297

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[knqyf263]

Since this conversion is needed in many places, we may want to define a utility function somewhere, like:

func NilIfEmpty[T any](s []T) []T {
    if len(s) == 0 {
        return nil
    }
    return s
}

[DmitriyLewen]

hm.. we already have this function 😄 :

trivy/pkg/x/slices/slices.go

Lines 3 to 8 in 60491f8

	func ZeroToNil[T any](t []T) []T {
	if len(t) == 0 {
	return nil
	}
	return t
	}

Used this function in 4f939b7

[knqyf263]

Oh, we already have it 😄