Add VTS tests for the untested ISupplicant methods.

Note that some methods such as getP2pInterface
are already tested implicitly by other tests.
Those methods are not tested in this file.

Bug: 386810503
Test: atest VtsHalWifiSupplicantTargetTest
Change-Id: I366ad5f9180f47dcd55ff60cc53f43eee6255bf9