MINOR: stats: report the SSL library FIPS mode in "show info"

MINOR: stats: report the SSL library FIPS mode in "show info"

The "SSL library FIPS mode" indicator printed by "haproxy -vv" had no
equivalent in the CLI. Add a "FipsMode" field to "show info" so that the
FIPS state of the running process can be queried at runtime, using the
same openssl_fips_mode() helper as the -vv line and the fips_mode()
configuration condition.

The field is only emitted by builds with SSL support, and reports 0 when
the SSL library is not in FIPS mode or does not support FIPS mode at all.