Add kernel-only provenance-discarding bcopy_data, memcpy_data, and
memmove_data APIs intended to copy raw data which does not contain
pointers (e.g., buffers on their way to or from network or storage
devices). On CHERI architectures, they will explicitly remove tags
from capabilities, removing any provenance. This reduces the risk of
accidental spread of pointers on CHERI system.
This includes a simple C implementation for CHERI targets.
Effort: CHERI upstreaming
Sponsored by: DARPA, AFRL, Innovate UK