Prepares hostapd for use by a wifi HAL vendor APEX

- Allows hostapd AIDL to read from an APEX for config files.
- Creates a cc_defaults with soong config vars for hostapd that
  customized implementations can override.
- Change -DCONFIG_HIDL to -DCONFIG_AIDL

Bug: 205065320
Test: m -j with mac80211_hwsim vendor APEX on Cuttlefish
Test: Connect to wifi and run hotspot
Change-Id: Id9937724a397d74c070a0b176c5ec0c18b71c9d1
3 files changed