Delete temporary file when ExportedImageTar construction fails

[wantaekchoi]

ExportedImageTar creates a temporary file in its constructor, copies the exported image into it, and then builds the layer factory from it:

ExportedImageTar(ImageReference reference, InputStream inputStream) throws IOException {
	this.tarFile = Files.createTempFile("docker-layers-", null);
	Files.copy(inputStream, this.tarFile, StandardCopyOption.REPLACE_EXISTING);
	this.layerArchiveFactory = LayerArchiveFactory.create(reference, this.tarFile);
}

The only caller relies on try-with-resources to clean the file up:

try (ExportedImageTar exportedImageTar = new ExportedImageTar(reference, response.getContent())) {
	exportedImageTar.exportLayers(exports);
}

If Files.copy or LayerArchiveFactory.create throws, the constructor fails after the temporary file has been created, so the instance is never assigned and close() never runs. LayerArchiveFactory.create does throw on a tar that has neither index.json nor manifest.json (Assert.state(...)), which can happen for a malformed or unexpected image export, and the docker-layers- file is then left behind in the temp directory.

This wraps the constructor body so the temporary file is deleted if either step fails, matching the cleanup already done in close().

This mirrors #50919, which fixed the same kind of leak in the buildpack platform and included a temp-file test; the new test in ExportedImageTarTests uses the same approach.