Prepare dependencies for the mainline
supplicant AIDL implementation.

This involves:
- Creating an apex_available version
  of wpa_supplicant_headers
- Moving the common AIDL header files
  to a shared directory
- Initializing the mainline supplicant
  AIDL library

Bug: 365585450
Test: m
Change-Id: I38e6c8f6999082ec964515cbc215bb8d5e3d47fa
6 files changed