Investigate DownloadManager and cleartextTrafficPermitted issues

[pocmo]

Colin mentioned this issue on Slack:
https://issuetracker.google.com/issues/114143692

The good news is that at least our component is not bound to the DownloadManager and we can toss it other implementations.

┆Issue is synchronized with this Jira Task

[buttercookie42]

Apart from some of the reasons mentioned here (using the same network stack as regular browsing for a more consistent experience w.r.t. certificates, proxies, etc., supporting one-time downloads that cannot be handed off externally once we've made the initial connection, ...), wouldn't that be one more reason for switching back to handling downloads ourselves in the medium term?

[pocmo]

@buttercookie42 In the long term we definitely want that. Just yesterday we talked about changing ContentDelegate.onExternalResponse() to something that gives us access to the WebResponse/stream directly instead of just the metadata. However there's too much on the roadmap to get to it right now; and we may need to rely on the DownloadManager a little longer.