wifi: add certificate HAL callback for Trust On First Use support

This API is used to pass the certificate returned from the server to
the framework.

Bug: 196180536
Test: atest VtsHalWifiSupplicantStaIfaceTargetTest \
            VtsHalWifiSupplicantStaNetworkTargetTest \
            VtsHalWifiSupplicantP2pIfaceTargetTest
Change-Id: I462008e8b2a0f18824b2886613f300213544c785