Add simulated GPIO ("board") LEDs. #38099

Job	Run time
build (base)	9m 8s
build (clang)	10m 58s
build-gcc-heli	8m 40s
autotest-heli (sitltest-heli)	13m 53s
autotest (sitltest-copter-tests1a)	12m 16s
autotest (sitltest-copter-tests1b)	13m 30s
autotest (sitltest-copter-tests1c)	15m 16s
autotest (sitltest-copter-tests1d)	12m 59s
autotest (sitltest-copter-tests1e)	13m 3s
autotest (sitltest-copter-tests2a)	13m 30s
autotest (sitltest-copter-tests2b)	32m 50s
	2h 36m 3s

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