Return NVMe device nodes/paths (/dev/...) robustly across nvme-cli schemas

[kanchansenlaskar]

Upstream change context:
- nvme-cli reworked nvme list -o json around v2.11, removing the
legacy top-level .Devices[].DevicePath and nesting device info under: Subsystems → Controllers → Namespaces.
- Reference discussion and breakage report: linux-nvme/nvme-cli#2749 (thread points to commit 929f461 as the change introducing the new JSON)
- Some distro builds may still emit DevicePath. This logic supports both.
- jq option is implemented to simplify parsing, but a pure-Python fallback is also provided if jq is not available on the target system. jq option is more efficient and robust, so it is preferred when possible.

[squirrelsc]

1. Move the parser logic into get_devices, so it can be shared, and managed in one place. get_devices should return a data structure, not a json object.
2. Place comments above the code line, not at the end.

[kanchansenlaskar]

1. Move the parser logic into get_devices, so it can be shared, and managed in one place. get_devices should return a data structure, not a json object.
2. Place comments above the code line, not at the end.

1. get_devices has always been returning a json object, as its job is to get us the details of devices. And that is the output consumed by many other functions in other files too. It has always been the job of the get_disks to parse it and fetch the device paths. Hence I changed the logic in get_disks and left get_devices as is.

2. That was the order even before, I will update it, also will change the content of that json.

[squirrelsc]

The method isn’t widely used—based on my search, it only shows up twice in this class. Also, the comment # raw ["Devices"] looks like a recent addition.