Add more tests and clean up helper (#3783)

Summary:
Added extension/evalue_util/test, extension/kernel_util/test, runtime/platform/test, kernels/portable/cpu/util/test
Clean up Test.cmake

Pull Request resolved: https://github.com/pytorch/executorch/pull/3783

Reviewed By: shoumikhin

Differential Revision: D58031811

Pulled By: kirklandsign

fbshipit-source-id: 4e5bbfcee486a2e0c1d9d9e596649bb9b6268443