Fix zpool provider get_pool_data parsing for ZFS 2.3.x zpool status output

[Nourdeo]

Fixes #94

This PR updates the zpool provider’s get_pool_data method to correctly
parse zpool status output on ZFS 2.3.x (while remaining compatible with ZFS
2.2.x).

ZFS 2.3.x changed the formatting of the vdev table: it now uses a
NAME STATE READ WRITE CKSUM header and space-indented rows instead of
tab-indented lines. The previous parsing logic (line.index("\t") == 0)
no longer matches, causing the provider to return an empty device list.

This patch:

• Finds the header line
• Collects the indented rows only
• Extracts the first column as the device/pool name
• Drops the NAME header from the final array

Tested on:

• ZFS 2.2.7-1~bpo12+1 → unaffected
• ZFS 2.3.2-2~bpo12+2 → provider now returns correct values

[CLAassistant]

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