REORG: sample: move the crypto samples to ssl_sample.c

REORG: sample: move the crypto samples to ssl_sample.c

These ones require openssl and are only built when it's enabled. There's
no point keeping them in sample.c when ssl_sample.c already deals with this
and the required includes. This also allows to remove openssl-compat.h
from sample.c and to further reduce the number of inclusions of openssl
includes, and the build time is now down to under 8 seconds.