zephyr: Add CONFIG_MCUBOOT_CLEANUP_RAM #2287

Job	Run time
environment (esp32, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secureb...	1m 56s
environment (esp32, serialrecovery)	1m 37s
environment (esp32s2, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	1m 47s
environment (esp32s2, serialrecovery)	1m 44s
environment (esp32s3, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	1m 51s
environment (esp32s3, serialrecovery)	1m 35s
environment (esp32c3, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	2m 12s
environment (esp32c3, serialrecovery)	1m 48s
environment (esp32, multi-image,multi-boot, multi)	1m 32s
environment (esp32s3, multi-image,multi-boot, multi)	1m 48s
	17m 50s

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