Forward TLS implementation selection to reqwest

[flxo]

The TLS implementation is selected by either feature use-rustls or use-native-tls. The selection of the TLS implementation is forwarded to the request dependency which otherwise defaults to native-tls.

[flxo]

CI fails with

 ---- some_outgoing_and_no_incoming_should_trigger_pings_on_time stdout ----
Polled = Ok(Incoming(ConnAck(ConnAck { session_present: false, code: Success })))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Outgoing(PingReq))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Incoming(PingResp))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Outgoing(Publish(0)))
Polled = Ok(Outgoing(PingReq))
Polled = Err(MqttState(AwaitPingResp))
thread 'some_outgoing_and_no_incoming_should_trigger_pings_on_time' panicked at 'called `Result::unwrap()` on an `Err` value: MqttState(AwaitPingResp)', rumqttc/tests/reliability.rs:133:42
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'some_outgoing_and_no_incoming_should_trigger_pings_on_time' panicked at 'called `Result::unwrap()` on an `Err` value: Custom { kind: ConnectionAborted, error: "connection closed by peer" }', rumqttc/tests/broker.rs:154:24

which is probably unrelated to this PR and a flaky test. Can someone retrigger please?

[de-sh]

Thanks for the PR @flxo 💯

[de-sh]

Hey @flxo, we have discovered that rumqttd no longer depends on reqwest, can you give us an idea of what was your usecase for which you had to make the changes included in this PR?

[flxo]

@de-sh I tried to build rumqttd for aarch64-linux-android with a cross container that doesn't include openssl. I turned off default features because I don't need TLS. Turned out that the reqwest dependency depended on native-tls.

Your're right. reqwest is not used anymore - should be fine to just remove it from the manifest of rumqttd.