comp/zstd: make bio_zstd_read return -1 on hard errors

comp/zstd: make bio_zstd_read return -1 on hard errors

Split NULL out param from zero outl. Return -1 on malloc failure and
NULL parameter. Keep 0 only for outl <= 0 and clean EOF. This lets
callers distinguish errors from empty reads without inspecting the
error queue.

Signed-off-by: Joshua Rogers <MegaManSec@users.noreply.github.com>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Paul Yang <paulyang.inf@gmail.com>
Reviewed-by: Todd Short <todd.short@me.com>
(Merged from https://github.com/openssl/openssl/pull/28908)