Tethering: Add WiGig support

This change is a combination of following changes:

1) Tethering: add TETHERING_WIGIG type
   Currently both WIFI and WIGIG use the same tethering type,
   TETHERING_WIFI. This causes conflicts between the frameworks,
   when both WIFI and WIGIG SoftAPs are started, one or both will
   not work.
   Fix this by using a seperate tethering type for WIGIG.

2) Tethering: remove TETHERING_WIGIG state machine on interface down
   The wigig state machine relies on a TETHERING_STATE_CHANGED broadcast
   that is sent when the tethering state machine is first created, during
   interface up. Currently the tethering state machine is not removed
   on interface down except for TETHERING_BLUETOOTH, and as a result
   wigig tethering only works the first time SoftAP is started.
   In order to fix this, remove the tethering state machine on interface
   down for TETHERING_WIGIG as well.

Bug: 143356416
Test: TetheringCoverageTests

Change-Id: Ic4d3aca0ed69234093af7f0206dab3335938c52a