databases/mysql80-server: Fix build with libressl

Upstream commit d737d2a [1] introduced three code paths for OpenSSL
<1.1, >=3.0 and between, none of which currently works with LibreSSL.
3.x APIs are not yet supported, and the code path for <1.1 directly
accesses struct members that were made opaque in LibreSSL as well.
Finally, the code path for >=1.1 uses DH_new_by_nid() which is missing
from LibreSSL.

Therefore add a patch introducing a fourth code path, doing essentially
the same as the version for OpenSSL <1.1, but using the accessor methods
instead of directly accessing struct members.

Also remove patches for viossl[factories].cc, which aren't needed any
more for current LibreSSL.

[1] https://github.com/mysql/mysql-server/commit/d737d2a3ef6fc82d933a2345769835e8c2e4f700

Approved by: joneum (maintainer, via private mail)
Differential Revision: https://reviews.freebsd.org/D42922