Fix wrongly initialized test key.

According to spec the test key has 32 bytes set to TextKeyBits::BYTE.
The VTS test and default implmementation only set the first 16 bytes and
left the remaining 16 bytes zero.

This bug fixes both, the VTS test and the default implementation.

Also some long overdue changes to how the auth token key is handled
by the generic operation.

Bug: 78456249
Test: VtsHalConfirmationUIV1_0TargetTest
Change-Id: I509f2c2a99704ee00625e6f6169479771a3bc17a