WIP syncing Bluetooth 5.1 keys

[aykevl]

I put a few hours in trying to sync BLE keys between macOS and Linux, but ultimately didn't succeed. The main blocker is the Services key which isn't part of NVRAM, and which BlueZ apparently doesn't update on connect.

I think the best way to implement this feature is by connecting to both systems manually, and then letting asahi-btsync update the BlueZ configuration based on the data stored in NVRAM. This hasn't been implemented yet though.

Maybe I'll continue working on this at some point, no guarantee. But for now, I'm just dropping this here so that hopefully someone will continue working on it (in other words, free to take!). The code is terrible and unusable in the current state, but I did reverse engineer most (probably all) important fields from NVRAM so at least that part doesn't need to be done again.

Background information:

• https://wiki.archlinux.org/title/Bluetooth#Dual_boot_pairing
• https://github.com/bluez/bluez/blob/master/doc/settings-storage.txt