Improve logging when running tosa_reference_model (#3120)

Summary:
* tosa_reference_model Log level is set from tosa_test_utils.py logger.
* Output stderr and stdout from tosa_reference process if it fails.

Change-Id: Id8588cbecd3aadbf5ec0c6a729a712212295ac6d

Pull Request resolved: https://github.com/pytorch/executorch/pull/3120

Reviewed By: cccclai

Differential Revision: D56820539

Pulled By: digantdesai

fbshipit-source-id: 14dce6043b1b1c5f58723ccea0903db906aee142