Motivated by: #4340.
I also activated
[`clippy::unnnecessary_wraps`](https://rust-lang.github.io/rust-clippy/master/#/unnecessary_wraps)
which does create some false-positives for the platform-specific code
but is IMO overall a net-positive. With the amount of Rust code and
crates increasing, it is good to have tools point out simplifications
like these as they are otherwise hard to spot, especially across crate
boundaries.
This adds an integration test that downloads a 10MB file from a server
and simulates the client roaming to another network while the download
is active.
We use a DNS resource for this to ensure it also doesn't take too long
in that case. DNS resources are what most users will be using and we
clear some internal DNS caches on connection failures. Hence, using a
DNS resource here is a somewhat roundabout way to test that we aren't
failing and re-establishing the connection but migrate it to a new
network path.