Make IHalAdapterVendorExtension stable and frozen

This allows to put its interface fragment into
framework VINTF and allows use AServiceManager_isDeclared
for detecting whether it is provided by SoC vendor.

Bug: 321651892
Bug: 323106963
Test: adb shell logcat | grep IHalAdapterVendorExtension
Change-Id: Ifa724eabf488d3f28e94074c588bf43d3bfb251c