hw/block/nvme: add simple copy command

Add support for TP 4065a ("Simple Copy Command"), v2020.05.04
("Ratified").

The implementation uses a bounce buffer to first read in the source
logical blocks, then issue a write of that bounce buffer. The default
maximum number of source logical blocks is 128, translating to 512 KiB
for 4k logical blocks which aligns with the default value of MDTS.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>