Bluetooth (and BLE) support

[jasta]

The Bluetooth landscape for Rust, especially embedded Rust, is very patchwork and it's preventing awesome projects like rs-matter from taking off by having a clear path to support BLE advertising/discovery (which is the only way for Matter devices to "just work"). I'm interested in trying to add generic traits (sync and async) for basic BLE support to start, followed by an esp32 implementation. Would it be too bold to try to take the embedded-ble namespace for the traits?

[jasta]

To be clear I think maybe we should add a section to the README talking about this context but before I submit a PR I'd like to collect feedback on the current state and problems. I'm interested in trying to fix them :)