AP_Stats: Only reset statistics if the user explicitly sets AP_Stats_… #35941

Job	Run time
build (stm32f7, chibios, 10)	4m 6s
build (stm32h7, chibios, 10)	3m 38s
build (fmuv2-plane, chibios, 10)	1m 52s
build (periph-build, chibios, 10)	3m 40s
build (iofirmware, chibios, 10)	1m 48s
build (CubeOrange-bootloader, chibios, 10)	51s
build (fmuv3-bootloader, chibios, 10)	56s
build (revo-bootloader, chibios, 10)	50s
build (stm32h7-debug, chibios, 10)	2m 31s
build (fmuv3, chibios, 10)	5m 26s
build (revo-mini, chibios, 10)	4m 3s
build (MatekF405-Wing, chibios, 10)	4m 21s
build (CubeOrange-ODID, chibios, 10)	2m 34s
build (CubeRedPrimary-bootloader, chibios, 10)	57s
build (configure-all, chibios, 10)	9m 43s
build (build-options-defaults-test, chibios, 10)	5m 53s
build (signing, chibios, 10)	2m 37s
build (CubeOrange-PPP, chibios, 10)	2m 2s
build (CubeOrange-SOHW, chibios, 10)	2m 2s
build (Pixhawk6X-PPPGW, chibios, 10)	1m 13s
	1h 1m 3s

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