Add performance tests for Euphonic+Brille+Horace

As mentioned in the testing results of [performance tests](https://github.com/pace-neutrons/brille-performance/blob/master/profile_summary.md) for Euphonic with Brille, the performance is lower when Euphonic is through via Horace than when it is run natively in Python.

This needs further investigations, and some of these tests should be included in the `pace-integration` repository.