fix: remove dependencies when parent folder is deleted

[SteveShani]

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What does this PR do?

When a file or folder is deleted, an entry that starts with .wh is created. Up until now, Snyk container detected files that were deleted, but not folders.

This change adds support for deleted folders by checking whether a file path starts with the path of the deleted folder. Meaning if we know that "/app/dependencies" was deleted, then a file path like "/app/dependencies/jar/library.jar" will be marked as deleted as well.

Where should the reviewer start?

Please see this PR: snyk/snyk-docker-plugin#568

How should this be manually tested?

To test this change, create an image from a dockerfile that:

• creates a folder
• downloads / copies a file that is recognized by Snyk (like .jar or package-lock.json) to that folder
• deletes the folder

Risk Assessment:

High - Changes are being made to remove dependencies from the dependency graph if we have detected that their parent folder was deleted. This change could result is false negatives.

Link to automated tests:

https://app.circleci.com/pipelines/github/snyk/snyk-docker-plugin/2684/workflows/e4e0cd59-fdce-46b8-91a3-e7bf78c42055