chore: Python 3.12 is the floor (NAPALM/driver-standard#6)

netOrk runs every driver in its own containers on Python 3.12, so 3.10
and 3.11 are no longer supported or tested. requires-python, mypy and
ruff move to 3.12, along with what ruff's pyupgrade rules then rewrite.

CHANGELOG.md

@@ -6,6 +6,10 @@ All notable changes to this driver. The format follows
 
 ## [Unreleased]
 
+### Changed
+- Python 3.12 is the floor (`requires-python = ">=3.12"`): netOrk runs every driver
+  on 3.12, so 3.10 and 3.11 are no longer tested (NAPALM/driver-standard#6).
+
 ### Fixed
 - `get_vpn_tunnels()` keys a WireGuard peer by its interface and the start of its
   public key (`wireguard-wg0-aBcD1234`, URL-safe) instead of its position, so a peer