AP_RangeFinder: Notify different alerts #42127

Job	Run time
build (base)	2m 40s
build (clang)	2m 3s
build-gcc-heli	2m 38s
autotest (sitltest-copter-tests1a)	7m 35s
autotest (sitltest-copter-tests1b)	9m 14s
autotest (sitltest-copter-tests1c)	11m 39s
autotest (sitltest-copter-tests1d)	8m 54s
autotest (sitltest-copter-tests1e)	8m 53s
autotest (sitltest-copter-tests2a)	9m 1s
autotest (sitltest-copter-tests2b)	30m 28s
autotest-heli (sitltest-heli)	10m 1s
	1h 43m 6s

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