Use ACRE2 to determine if data can be transmitted between units

[jetelain]

Create an option to integrate ACRE2: Transmit data between unit/vehicle only if both has a radio, and ask ACRE2 to determine if transmission is good enough (-100dbm minimum).
Use a predefined/hardcoded frequency.

acre_sys_signal_fnc_getSignal can be used, but is not public

[mrschick]

Using a non-public function should only be an issue if we are worried of compatibility being broken in the future, which seems extremely unlikely in well-developed mods like ACRE.

The developer behind HEMTT started working on a realistic BFT framework limited to ACRE2 radios some time ago, he also used acre_sys_signal_fnc_getSignal
https://github.com/BrettMayson/aid/blob/4061c7571f20e3a055820ed26e7113b48077b518/addons/network/functions/fnc_tickRadioSignal.sqf#L37