Clarify compressed zfs send/recv behavior

Docs for send and receive do not explain behavior when sending a
compressed stream then receiving on a host that overrides compression
with -o compress=value.

The data from the send stream is written as it was from the send is
the compressed form but the compression algorithm set on the receiver
is the overridden version which causes some confusion as to what
algorithm was actually used.

Updated man docs to clarify behavior

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed By: Allan Jude <allanjude@freebsd.org>
Signed-off-by: manfromafar <manfromafar@outlook.com>
Closes #11690