Added bootloader_common_get_sha256_of_partition() and esp_partition_get_sha256() - get or calculate SHA-256
digest for app and data partitions.
Added bootloader_sha256_hex_to_str() - helps to print SHA-256 digest
Added esp_partition_check_identity() - compares two partitions by SHA-256 digest
Refactoring a function esp_image_load() in bootloader space to esp_image_verify() and
bootloader_load_image(). Old name function esp_image_load is deprecated
and will remove in V4.0 version.
spi_flash/sim: Fix error test_host. Add stub for bootloader_common_get_sha256_of_partition in sim/stubs
