psh: reimplement 'kill' command #954

Job	Run time
call-ci / build (armv7a7-imx6ull-evk)	1m 11s
call-ci / build (armv7a9-zynq7000-qemu)	1m 31s
call-ci / build (armv7a9-zynq7000-zedboard)	1m 1s
call-ci / build (armv7a9-zynq7000-zturn)	1m 2s
call-ci / build (armv7m4-stm32l4x6-nucleo)	1m 10s
call-ci / build (armv7m7-imxrt105x-evk)	1m 15s
call-ci / build (armv7m7-imxrt106x-evk)	1m 12s
call-ci / build (armv7m7-imxrt117x-evk)	1m 12s
call-ci / build (host-generic-pc)	58s
call-ci / build (ia32-generic-pc)	1m 1s
call-ci / build (ia32-generic-qemu)	1m 1s
call-ci / build (riscv64-generic-qemu)	1m 6s
call-ci / build (riscv64-generic-spike)	1m 12s
call-ci / build (sparcv8leon3-gr716-mini)	1m 7s
call-ci / test HW (armv7a7-imx6ull-evk)	5m 43s
call-ci / test HW (armv7m7-imxrt106x-evk)	2m 27s
call-ci / test EMU (armv7a9-zynq7000-qemu)	9m 14s
call-ci / test HW (armv7m7-imxrt117x-evk)	2m 44s
call-ci / test EMU (host-generic-pc)	1m 1s
call-ci / test HW (armv7a9-zynq7000-zedboard)	5m 52s
call-ci / test EMU (ia32-generic-qemu)	5m 59s
call-ci / test HW (armv7m4-stm32l4x6-nucleo)	9m 54s
call-ci / test EMU (riscv64-generic-qemu)	5m 17s
call-ci / tests-summary	11s
call-ci / send-notification	0s
	1h 4m 21s

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