examples: Update Rust examples for buttplug v6

[brandonweeks]

Follow up to #54. I was mostly able to migrate the example code to the v6 API, however I have a few questions about device_control.rs:

• server::comm_managers::test::new_bluetoothle_test_device was moved to tests::util::test_device_manager and no longer appears visible to other crates.
• ClientDeviceMessageAttributesMap was refactored into the ClientDeviceMessageAttributes struct and I cannot find an ergonomic way to implement loop over the supported messages and attributes (device_control.rs line 55-63 in this PR).

I'm by no means a Rust expert, so apologies if these issues should be simple.

[qdot]

Heads up, I'm rebuilding the docs site in docusaurus over here: https://github.com/buttplugio/docs.buttplug.io. The site itself is already up at https://docs.buttplug.io, just haven't really announced it yet 'cause I'm trying to finish out more stuff.

As I've been spending this week updating the C# and JS examples, I'm gonna bring what's done of the v6 rust examples in this PR in over there, and I'll handle the changes mentioned.

But, to answer the questions here anyways:

For bluetooth_test_device: I'm swapping this out with websocket devices, which I've written a new section on.

For Message Attributes: Yeah I've started mapping things to objects since we don't really have a lot of message additions right now. I now expose this via handing out attributes to the various ways to do things. I'm gonna have to add some convenience methods to the rust impl that I've already put in C#/JS that should make it easier to reason about.