Remove NetworkManager + DBus rom WiFi stack

[adeebshihadeh]

Following in the spirit of #37277. Faster connect times, simpler stack, and tinier AGNOS.

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Bounty targets

• All of openpilot works
• Works on both comma 3X and comma four
• Zero dbus/jeepney/NetworkManager in the WiFi code path
• At least 10 Discord users run it for a week and sign off on it, with and without tethering

Misc notes:

• Routing priority still needs to work properly (e.g. WiFi > LTE when both are up)
• Doesn't require a new AGNOS; code change can land first, then just drop NM from the next AGNOS build
• On-disk storage can stay as .nmconnection for easy rollback and interop with existing saved networks
• I did a quick attempt in bye bye NetworkManager #37662 that can be used as a reference
  • this implementation isn't complete though. for example, if the ui process dies, you lose networking.

Bonus target ($500): Connect time (to IP) must be strictly faster than NetworkManager on a known WPA2 network, measured over 5 iterations on device.

[adeebshihadeh]

Locked to @andiradulescu