[Passpoint] Add API to check if Passpoint T&C is supported

Add API to check if Passpoint T&C is supported, to allow
provisioning apps to avoid suggesting networks that are gated by
T&Cs acceptance, in devices that do not support this feature and
could never connect.

Bug: 181581415
Test: atest WifiManagerTest
Change-Id: Ic764edb39007e05b371f37296f619a0f003690d8
4 files changed