* Use AMbyteSpan for byte values
Before this change there was an inconsistency between AMmapPutString
(which took an AMbyteSpan) and AMmapPutBytes (which took a pointer +
length).
Either is fine, but we should do the same in both places. I chose this
path to make it clear that the value passed in was an automerge value,
and to be symmetric with AMvalue.bytes when you do an AMmapGet().
I did not update other APIs (like load) that take a pointer + length, as
that is idiomatic usage for C, and these functions are not operating on
byte values stored in automerge.
b05c9e83a4