Add a new utility class wifi_hidl_test_utils_1_6

for the Wifi VTS tests.

Main method is getBridgedWifiApIface_1_6, which
allows us to configure the chip based on the
Bridged AP IfaceConcurrencyType, rather than
the AP IfaceType like in getBridgedWifiApIface_1_5.

Implementations were largely copied from
wifi_hidl_test_utils and wifi_hidl_test_utils_1_5.

Bug: 283402709
Test: atest VtsHalHostapdTargetTest
       # tested on a Bluejay device that supports
       # the AddAccessPointWithDualBandConfig test
Change-Id: I2571876149fc14c8de02e1cec9934dd052cada5c