bootloader_support: move embedding key after component registration
bootloader_support: move embedding key after component registration

Bootloader build requires verification key to be embedded in the binary.
Under specific configs, this key is generated during build time from the
signing key. Move the key generation to after the component
registration, since non scriptable commands are used in the process
(during early expansion)

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf