`Stream` will be qualified as `AK::Stream` until we remove the
`Core::Stream` namespace. `IODevice` now reuses the `SeekMode` that is
defined by `SeekableStream`, since defining its own would require us to
qualify it with `AK::SeekMode` everywhere.
Until we can get our own RequestServer infrastructure up and running,
running the TLS and HTTP code in-process was causing lots of crashes
due to unexpected reentrancy via nested event loops.
This patch adds a simple backend for HTTP and HTTPS requests that simply
funnels them through QNetworkAccessManager.
