functestlib: harden nmcli Wi-Fi connect with key-mgmt fallback profile

[smuppand]

Some images return the following when using the “simple” NetworkManager path:

nmcli dev wifi connect password
Error: 802-11-wireless-security.key-mgmt: property is missing.
This PR makes wifi_connect_nmcli() resilient to that case while preserving current behavior on images where the simple path works.

What changed

• Keep the existing “simple connect” attempt (with retries).
• If it fails with the key-mgmt property is missing error (or similar NM error):
• Ensure Wi-Fi is enabled and device is managed: nmcli r wifi on, nmcli dev set managed yes.
• Disconnect and rescan the SSID.
• Remove any stale connection with the same name.
• Create an explicit profile:
• WPA2/PSK: wifi-sec.key-mgmt wpa-psk, wifi-sec.psk
• Fallback to WPA3/SAE (wifi-sec.key-mgmt sae) if WPA2 creation/bring-up fails.
• Open networks (no password): wifi-sec.key-mgmt none.
• Bring the profile up: nmcli con up .
• All nmcli output is logged to ${LOG_DIR:-.}/nmcli__.log for triage.
• The function returns success on the first working method; otherwise bubbles up failure.
• No changes required for callers; function name and signature unchanged.

Why this is safe

• Only triggers the profile path when the simple path fails with the specific NM error.
• Does not change flow for already-working environments.
• Avoids echoing the PSK into logs (only nmcli’s output is captured).

[vnarapar]

LGTM