AP_Common: Location: add set_alt_m #43476

Job	Run time
build (stm32f7, chibios, 10)	12m 52s
build (stm32h7, chibios, 10)	11m 33s
build (fmuv2-plane, chibios, 10)	6m 8s
build (periph-build, chibios, 10)	8m 33s
build (iofirmware, chibios, 10)	3m 44s
build (CubeOrange-bootloader, chibios, 10)	3m 1s
build (fmuv3-bootloader, chibios, 10)	3m 3s
build (revo-bootloader, chibios, 10)	2m 58s
build (stm32h7-debug, chibios, 10)	7m 45s
build (fmuv3, chibios, 10)	14m 23s
build (revo-mini, chibios, 10)	11m 35s
build (MatekF405-Wing, chibios, 10)	11m 53s
build (CubeOrange-ODID, chibios, 10)	8m 53s
build (CubeRedPrimary-bootloader, chibios, 10)	2m 58s
build (configure-all, chibios, 10)	12m 49s
build (build-options-defaults-test, chibios, 10)	21m 54s
build (signing, chibios, 10)	8m 39s
build (CubeOrange-PPP, chibios, 10)	7m 24s
build (CubeRed-EKF2, chibios, 10)	7m 21s
build (SOHW, chibios, 10)	11m 24s
build (Pixhawk6X-PPPGW, chibios, 10)	4m 0s
build (new-check, chibios, 10)	13m 9s
	3h 15m 59s

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