zephyr: Add CONFIG_MCUBOOT_CLEANUP_RAM #2296

Job	Run time
environment (esp32, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secureb...	1m 51s
environment (esp32, serialrecovery)	1m 27s
environment (esp32s2, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	1m 48s
environment (esp32s2, serialrecovery)	1m 38s
environment (esp32s3, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	1m 46s
environment (esp32s3, serialrecovery)	1m 35s
environment (esp32c3, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	1m 52s
environment (esp32c3, serialrecovery)	1m 25s
environment (esp32, multi-image,multi-boot, multi)	1m 40s
environment (esp32s3, multi-image,multi-boot, multi)	1m 48s
	16m 50s

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