Implement nickel_bluetooth action

[onatbas]

Implementation of a new action "nickel_bluetooth" to turn Bluetooth on and off via NickelMenu.

Available commands are:
enable
disable
toggle

I've been testing/using this modified version of NickelMenu on my Clara 2E and It should be compatible with all Bluetooth devices.

This should address issue #142

Usage examples:
menu_item :main :Bluetooth (enable) :nickel_bluetooth :enable
menu_item :main :Bluetooth (disable) :nickel_bluetooth :disable
menu_item :main :Bluetooth (toggle) :nickel_bluetooth :toggle

[pgaskin]

Look okay overall, not tested (I don't have a Kobo with bluetooth support).

A few minor formatting nitpicks (I should add clang-format at some point).

Also, add the //libnickel symbol checks with the version constraints for CI.

[onatbas]

Thanks. I identified a few problems with the internal Bluetooth driver: in certain conditions, the connection doesn't get established if BT is turned on and off too quickly. I added a few actions and parameters to this fix this and currently testing the changes.
In addition to addressing your comments, I shall submit my changes by the end of today.

[onatbas]

I have completed my checks and happy with the current implementation of this feature. The //libnickel checks could probably go even earlier versions but, I haven’t had the chance to validate all versions.
let me know if there are other changes, style adjustments I may have missed.

[pgaskin]

Looks perfect; I like how you organized the actions. I can't test it as I don't have one which supports it, but it's simple enough, I'll probably just merge it.

[onatbas]

I'm glad you like it. It's an old pattern called "bitmasking" or "bit flags." The method was going toward multiple booleans, and this pattern is intended for that problem.

It is indeed very simple as you quite rightly put it. Here's a sample from my Clara 2E. (Bluetooth device blinks when it's disconnected/scanning. When the blinking stops, it means connection established.)
https://github.com/pgaskin/NickelMenu/assets/714795/f6f404ee-7f92-45ad-90be-0bd51cd4ea35