[AWARE] Remove support for vendor-specific attributes

Vendor-specific attribute support API is not fully functional or
thought out. The Tx portion is working but the Rx portion requires
additional configuration to prevent spamming the framework with all
vendor-specific attributes.

Remove until full solution is designed.

Bug: 35193235
Test: unit tests and integration (sl4a) tests.
Change-Id: I31a601af3b2c1f9f736130ce00abf73c55ac086a