[Passpoint] Support for Terms & Conditions

Added framework support for Terms & Conditions. Handle the
WNM-notification and extract the URL. Reject invalid and non-HTTPS
URLs (block these networks since there will be no access without
accepting the T&Cs).

Bug: 171928337
Test: atest ClientModeImplTest PasspointManagerTest
Change-Id: Iaf161d258f7768337f919aeaf27174742c541a1f
4 files changed