wifi(implementation): Pin primary STA iface to wlan0

The primary STA iface will always be pinned to wlan0.
The primary AP iface will be pinned to wlan0 for devices not supporting
STA + AP concurrency & wlan1 for devices supporting STA + AP concurrency.

All secondary STA or AP ifaces will be allocated on a first come first
service basis (the current logic).

Also, refactored/renamed some of the iface combo selection logic methods
to help check whether concurrency is allowed in the current mode.

Bug: 128946563
Test: ./data/android.hardware.wifi@1.0-service-tests
Test: Will send for full regression tests.
Test: On crosshatch, ensured that STA always comes up on wlan0 & AP
comes up on wlan1 regardless of the sequence of toggle followed.
Change-Id: Idca8de42ce819240bf0fac2a9039d15ed4bcaf90