Add openssl 3.0 interop tests

The plan is to retire the 1.0.2 interop tests soon so as to be able to
drop the dead and dangerous OpenSSL 1.0.2 port.

The cert part is extremely slow on arm64: the whole interop test on an m1
is about 10x slower (~45 min!) than on a modern amd64 laptop, so people
running regress may want to wait a bit with adding OpenSSL 3 to their test
boxes until this is sorted out.