Separate aten and portable tests in memory_planning_ops (#3873)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/3873

In opt build mode, we can't link both aten and portable pybindings. Duplicate symbols failures.

https://www.internalfb.com/intern/test/562950098227943?ref_report_id=0

Let's separate into two different tests. This will be good in the long term because we will only enable the portable in OSS anyway.

Reviewed By: Gasoonjia

Differential Revision: D58246232

fbshipit-source-id: e18633f85c40595b6b5466fdd3808b64fea033cf