Rewrite gpu_index_test to don't be a change detector test.
Rewrite gpu_index_test to don't be a change detector test.

Also get rid of unnecessary HloModuleConfigs. The method from the base class
already adds those. Fix one test that had invalid layouts.
Remove one TENSORFLOW_USE_ROCM guard that most likely isn't doing anything
(we don't define it in the build target).
