west.yml: Update zcbor to v. 0.5.1

lwm2m: Regenerate lwm2m_senml code from the CDDL description.
Reapply manual changes.
Create a sh script to perform the regeneration.

tests: zcbor_bulk: Adapt to zcbor 0.5.1
zcbor_new_decode_state() now has no return value.

Signed-off-by: Øyvind Rønningstad <oyvind.ronningstad@nordicsemi.no>