Green on Linux should check power saving status of Jade

On a more modern Linux such as Fedora, a default power saving config option prevents newer Jade units from being able to communicate with the Green app, causing it to crash. Older Jades are unaffected because they have a different serial chip.

We should query if the power saving feature is enabled or not and provide an alert to the user that points them to instructions (I'm thinking [here](https://help.blockstream.com/hc/en-us/articles/900005443223-Why-is-Blockstream-Jade-not-recognized-by-my-computer-) is a good home) for how to install appropriate udev rules that disable this feature every time the Jade is plugged into the host machine.

To check if a Jade is plugged in we can look to see if `/dev/ttyACM0` exists and then proceed to determining if power saving is enabled.

It's possible for a non-root user to query the state of the power saving feature, even when inside a Flatpak sandbox:

```
$ cat /sys/bus/usb/devices/1-2/power/control
auto
```
Note this path is dependent on the user's machine and is very likely to be different across different sets of hardware. But, we can (again, as non-root user) look in each device subdirectory for the `idProduct` and `idVendor` files which contain the product and vendor IDs and see if we can find Jade's:

```
$ pwd
/sys/bus/usb/devices

$ ls -la */idProduct*
-r--r--r--. 1 root root 4096 May 30 07:36 1-10/idProduct
-r--r--r--. 1 root root 4096 May 30 07:36 1-7/idProduct
-r--r--r--. 1 root root 4096 May 30 07:36 1-8/idProduct
-r--r--r--. 1 root root 4096 May 30 07:36 3-1/idProduct
-r--r--r--. 1 root root 4096 May 30 07:36 usb1/idProduct
-r--r--r--. 1 root root 4096 May 30 07:36 usb2/idProduct
-r--r--r--. 1 root root 4096 May 30 07:36 usb3/idProduct
-r--r--r--. 1 root root 4096 May 30 07:36 usb4/idProduct

$ cat 1-10/idProduct
01a2

This particular device is not Jade :(. On to the next one...
```
I've tested the udev rule below (placed in `/etc/udev/rules.d/21-jade.rules`) on a couple different Fedora machines successfully.

```
ATTRS{idProduct}=="55d4", ATTRS{idVendor}=="1a86", SUBSYSTEM=="usb", TEST=="power/control" ATTR{power/control}="on"
```
This will turn off the power saving automatically any time a Jade is plugged in.

Older Linux distros like Ubuntu 22.04 do not enable the power saving OOTB and are unaffected by this, but future versions might. It's unclear if it's a difference between Linux kernel versions or their configs or if Ubuntu is intentionally turning this off and Fedora leaves it untouched, so it's a good idea to tackle this ahead of time.