Add IfaceConcurrencyType and related methods for AP_BRIDGED concurrency

Add IfaceConcurrencyType to represent Iface implementations that
have different concurrency implications for the same IfaceType, such as
Bridged AP and Single AP for IWifiApIface. Add a new IWifiChip HAL API,
getAvailableModes_1_6 to return the new concurrency type combos.

Bug: 207055799
Test: 1.6/default/tests/runtests.sh
Change-Id: Iad20a3d95d54dd8b624db912fd3153c2a3372f45