Fix EVS VTS test cases

- Correctly handle a payload of EvsEventDesc type variables.
- Explicitly duplicate buffers to hold.
- Proeprly handle ultrasonic APIs that are not implemented yet.

Bug: 226628778
Test: atest VtsHalEvsTargetTest on Seahawk
Change-Id: I4c202b171d6cc905732e0687743cb481893a6dd2