Refactor RGG tests to use TestModel utilities.

Before this change, the RGG has its own logic creating a NDK
model/request, and comparing the final results. This CL makes RGG to
adopt the new TestModel utilities.

Fixes: 139442221
Bug: 150805665
Test: NNT_static
Test: NNT_static_fuzzing
Change-Id: I041f45026ed271abad4632abd7ec5360f432efda
Merged-In: I041f45026ed271abad4632abd7ec5360f432efda
(cherry picked from commit 53fb979943af6671ff581dcca5cf53a7818d1e74)
6 files changed