feat: read-only IPMI driver; report a missing Redfish license (0.2.0)

A Supermicro X10DRL-i refuses Redfish without a license (SUM, DCMS or
OOB), even the service root. IPMI answers without one.

- New entry point `ipmi` (napalm_redfish.ipmi.IpmiDriver) on
  ManagementControllerDriver, over pyghmi: facts and inventory from the
  FRU (serial number, system UUID), the BMC's LAN interface, sensors
  (temperatures, fans, power supplies), the power state, the event log
  and the BMC firmware. Read-only: no power control, no BMC reset.
  Tested against recordings of the X10 with serials, the UUID, MACs and
  IPs replaced.
- RedfishDriver.open() no longer fails on a license refusal: get_facts
  returns what is known without Redfish, get_device_warnings reports
  bmc_license_required with the licenses the BMC names, every other
  getter raises. netOrk then shows the reason instead of an offline BMC.
- IpmiDriver is not exported from the package: NAPALM's own
  get_network_driver("redfish") takes the first driver class of
  napalm_redfish.

tests/fixtures/supermicro-x10drl-i-3.91/COMMANDS.txt

@@ -4,3 +4,9 @@ without a Supermicro license. Requests were made without credentials.
 service_root_403.json   GET /redfish/v1/   -> HTTP 403, Content-Type application/json
 landing_page.html       GET /              -> HTTP 200, the BMC web login page (trimmed to
                                               the head and the login form action)
+
+ipmi/   Read over IPMI 2.0 (pyghmi 1.6, lanplus) with a BMC account, 2026-10-13. One file per
+        pyghmi call: power (get_power), net_configuration (get_net_configuration),
+        firmware (get_firmware), inventory (get_inventory), sensors (get_sensor_data,
+        each SensorReading's attributes), health (get_health), event_log (get_event_log).
+        Serial numbers, the system UUID, MAC addresses and IPs are replaced by placeholders.