Use streams to download attachments directly to disk

Co-authored-by: trevor-signal <131492920+trevor-signal@users.noreply.github.com>

ts/test-node/types/EmbeddedContact_test.ts

@@ -165,6 +165,7 @@ describe('Contact', () => {
           avatar: fakeAttachment({
             pending: true,
             contentType: IMAGE_GIF,
+            path: undefined,
           }),
         },
       };