boot: Add MCUBOOT_HW_KEY support for image encryption #1758

Job	Run time
config (RELEASE 2,4,6 SIGNATURE)	8m 55s
config (RELEASE 2,4,6 SIGNATURE LOW)	13m 22s
config (RELEASE 2,4,6 SIGNATURE MEDIUM)	17m 11s
config (RELEASE 8,10 SIGNATURE)	6m 25s
config (RELEASE 8,10 SIGNATURE LOW)	9m 14s
config (RELEASE 8,10 SIGNATURE MEDIUM)	12m 1s
config (MINSIZEREL 2,4,6 SIGNATURE)	14m 53s
config (MINSIZEREL 2,4,6 SIGNATURE LOW)	19m 52s
config (MINSIZEREL 2,4,6 SIGNATURE MEDIUM)	23m 36s
config (MINSIZEREL 8,10 SIGNATURE)	10m 22s
config (MINSIZEREL 8,10 SIGNATURE LOW)	13m 30s
config (MINSIZEREL 8,10 SIGNATURE MEDIUM)	16m 15s
	2h 45m 36s

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