Package tracing PoC

[another-rex]

Package/vulnerability tracing capability, used to determine which layer introduced a vulnerability.

This required some minor refactoring of the experimental image scanning types.

TODOs:

• [x] Perform error handling when attempting to parse older layer files.
• [ ] Determine the best way to pass back up the layer information.
• [x] Add tests

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.12291% with 32 lines in your changes missing coverage. Please review.

Project coverage is 65.47%. Comparing base (e619fcc) to head (992687f). Report is 1 commits behind head on main.

Files	Patch %	Lines
internal/image/image.go	73.77%	15 Missing and 1 partial :warning:
internal/image/scan.go	85.71%	7 Missing and 3 partials :warning:
internal/image/extractor.go	70.00%	2 Missing and 1 partial :warning:
internal/image/layer.go	89.28%	2 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1049 +/- ## ========================================== + Coverage 65.32% 65.47% +0.15% ========================================== Files 150 150 Lines 12529 12636 +107 ========================================== + Hits 8184 8274 +90 - Misses 3884 3897 +13 - Partials 461 465 +4 ```

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