VTS tests for IWifiStaIface@1.2.

Note that the new test is currently disabled because we have no
meaningful way to test wifi interfaces that require the interface to be
in connected state. For the full story, read the TODOs above the test.

Change-Id: Iad7abd1f04a9ac6ca60e675222fbd2a893cb4072
Bug: 71581915
Bug: 73804303
Test: as follows:
    m VtsHalWifiV1_2TargetTest
    adb sync data
    adb shell /data/nativetest64/VtsHalWifiV1_2TargetTest/VtsHalWifiV1_2TargetTest