AP_Stats: Make cumulative flight time updates optional #33580

Job	Run time
build (stm32f7, chibios, 10)	5m 18s
build (stm32h7, chibios, 10)	4m 28s
build (fmuv2-plane, chibios, 10)	2m 39s
build (periph-build, chibios, 10)	6m 1s
build (iofirmware, chibios, 10)	1m 42s
build (CubeOrange-bootloader, chibios, 10)	49s
build (fmuv3-bootloader, chibios, 10)	56s
build (revo-bootloader, chibios, 10)	56s
build (stm32h7-debug, chibios, 10)	2m 59s
build (fmuv3, chibios, 10)	7m 37s
build (revo-mini, chibios, 10)	6m 24s
build (MatekF405-Wing, chibios, 10)	6m 34s
build (CubeOrange-ODID, chibios, 10)	3m 43s
build (CubeRedPrimary-bootloader, chibios, 10)	1m 9s
build (configure-all, chibios, 10)	8m 53s
build (build-options-defaults-test, chibios, 10)	9m 20s
build (signing, chibios, 10)	3m 30s
	1h 12m 58s

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