feat(netbench): add built-in drivers

[camshaft]

Description of changes:

This change adds netbench drivers for s2n-quic, native-tls, and tcp. s2n-tls will be added after the async bindings are available.

I added a README on how to run one of the drivers locally. This will change after I get the CLI working, but should be enough to get an idea of how to run it.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[toidiu]

non-blocking: curious what the Thread abstraction is for. Are you simulating multi-threaded behavior? Pausing and restating threads?

It also seems like you are using HashSet as a checkpoint. What exactly is a checkpoint, and how are you using a u64 to control pause and go logic?

[camshaft]

Are you simulating multi-threaded behavior? Pausing and restating threads?

Yeah the scenario can have "threads" which are just concurrently executing tasks. For example:

s2n-quic/netbench/netbench-scenarios/src/request_response.rs

Lines 84 to 88 in 483667d

	conn.scope(|scope| {
	for _ in 0..count {
	scope.spawn(request);
	}
	});

What exactly is a checkpoint, and how are you using a u64 to control pause and go logic?

It's just a way for one scenario thread to unblock another. For example, let's say we want to start sending on another stream after we've sent 1 MB:

s2n-quic/netbench/netbench/src/scenario/builder/tests.rs

Lines 53 to 82 in 483667d

	let (cp1_rx, cp1_tx) = conn.checkpoint();
	conn.concurrently(
	|conn| {
	conn.open_send_stream(
	|local| {
	local.set_send_rate(10.kilobytes() / 50.millis());
	local.send(1.megabytes() / 2);
	local.unpark(cp1_tx);
	local.send(1.megabytes() / 2);
	},
	|peer| {
	peer.set_receive_rate(10.kilobytes() / 50.millis());
	peer.receive(1.megabytes());
	},
	);
	},
	|conn| {
	conn.open_send_stream(
	|local| {
	local.park(cp1_rx);
	local.set_send_rate(1024.bytes() / 50.millis());
	local.send(1.megabytes());
	},
	|peer| {
	peer.set_receive_rate(1024.bytes() / 50.millis());
	peer.receive(1.megabytes());
	},
	);
	},