This VSC enable host-initiated role-switching after connection.
Implement this VSC in a driver fashion.
Test: avatar security_test with the Bluetooth Dongle Intel BE200
Further adventures in porting tools to Rust to flesh out the supported
API.
These tools didn't feel like `example`s, so I made a top level `bumble`
CLI tool that hosts them all as subcommands. I also moved the usb probe
not-really-an-`example` into it as well. I'm open to suggestions on how
best to organize the subcommands to make them intuitive to explore with
`--help`, and how to leave room for other future tools.
I also adopted the per-OS project data dir for a default firmware
location so that users can download once and then use those .bin files
from anywhere without having to sprinkle .bin files in project
directories or reaching inside the python package dir hierarchy.
