AP_HAL_SITL: allow disabling CAN interfaces #31580

Job	Run time
build (chibios, Durandal)	19m 5s
build (chibios, MatekF405)	17m 24s
build (chibios, KakuteF7)	15m 44s
build (chibios, MatekH743-bdshot)	19m 12s
build (chibios, Pixhawk1-1M)	17m 28s
build (chibios, MatekF405-CAN)	3m 54s
build (chibios, DrotekP3Pro)	4m 1s
build (chibios, Hitec-Airspeed)	5m 2s
build (chibios, f103-GPS)	5m 12s
build (disco, armhf)	15m 42s
	2h 2m 44s

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