Address extraction edge cases re: duplicate file names

[egibs]

More fallout from scanning Sonarqube.

There are five files of interest in this package:

./linux-x64-musl/node.xz
./linux-x64/node.xz
./win-x64/node.exe.xz
./darwin-arm64/node.xz
./sonarjs-1.0.0.tgz

Our original extraction logic would only process one of the extracted node files because only the file name (node) was stored in the extracted file map. Additionally, extracting the files would fail with legitimate EOF errors and this was also happening with the sonarjs-1.0.0.tgz file. There was also an opportunity to clean up the awkward extractedFiles map ranging and replace it with filepath.WalkDir.

This PR addresses this edge case, decompresses files in such a way to preserve their parent directory, and removes archive types from supportedKind which causes weird behavior. Instead, we can return a non-nil FileType if a given path's extension is present in the archive map.

The test files being erased is expected; these files are actually tar files for some reason (?) and removing tar from supportedKind means they aren't scanned directly.

[eslerm]

appreciate simplifications :)