WifiConfiguration: Add support for auto-selecting AP band

Add new constant indicating the band/channel for SoftAp operation will
be determined during softap initialization.

The term 'ANY' for this option to be consistent with terminology used
in hostapd.

Bug: 68763822
Test: Compiles
Change-Id: I9676caf5188601ca16c9229aaa8be2d0e43404a6