Remove support for OpenSSL older than 1.1.0

Remove support for OpenSSL older than 1.1.0

OpenSSL 1.0.2 has been EOL from the upstream OpenSSL project for
some time, and is no longer the default OpenSSL version with any
vendor which package PostgreSQL. By retiring support for OpenSSL
1.0.2 we can remove a lot of no longer required complexity for
managing state within libcrypto which is now handled by OpenSSL.

Reviewed-by: Jacob Champion 
Reviewed-by: Peter Eisentraut 
Reviewed-by: Michael Paquier 
Discussion: https://postgr.es/m/[email protected]
Discussion: https://postgr.es/m/CA+hUKGKh7QrYzu=8yWEUJvXtMVm_CNWH1L_TLWCbZMwbi1XP2Q@mail.gmail.com