HS 2.0 server: RADIUS server support for SIM provisioning

HS 2.0 server: RADIUS server support for SIM provisioning

This adds support for hostapd-as-RADIUS-authentication-server to request
subscription remediation for SIM-based credentials. The new hostapd.conf
parameter hs20_sim_provisioning_url is used to set the URL prefix for
the remediation server for SIM provisioning. The random
hotspot2dot0-mobile-identifier-hash value will be added to the end of
this URL prefix and the same value is stored in a new SQLite database
table sim_provisioning for the subscription server implementation to
use.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>