OpenSSL: Use pkcs11-provider when OPENSSL_NO_ENGINE is defined

OpenSSL: Use pkcs11-provider when OPENSSL_NO_ENGINE is defined

Now that ENGINE API starts being deprecated in distros (like Fedora [1])
wpa_supplicant users might need a way to load certificates and keys from
PKCS11 URIs even when OPENSSL_NO_ENGINE is defined. We can do that using
pkcs11-provider: load it by default in wpa_supplicant, and try to use it
when OPENSSL_NO_ENGINE is defined and configuration requests PKCS11 URIs
for certificates / keys.

Inspired by pkcs11-provider test program 'tlssetkey.c' [2]

[1] https://fedoraproject.org/wiki/Changes/OpensslDeprecateEngine
[2] https://github.com/latchset/pkcs11-provider/blob/main/tests/tlssetkey.c

Signed-off-by: Davide Caratti <davide.caratti@gmail.com>