Add a performance test

[jiayingqi]

Hi @jorgensd, thanks for the huge work done for the FEniCSx. As one of the many users of FEniCS/FEniCSx, I really think at least two points of FEniCSx are attracting: (1) convenience for solving PDEs and (2) the high computational efficiency based on parallel computation. I think the first point is already well illustrated in this tutorial. However, it would be better to illustrate the computational efficiency of FEniCSx versus other software such as Matlab.

[jorgensd]

This is out of the scope of the tutorials. As the tutorials are hosted on binderhub, I cannot access enough processes to illustrate performance.

additionally, comparing to other software is an «infinite» task. There are a large variety of FEM software out there, written in Fortran, C++, C, Matlab, Julia etc. A tutorial cannot cover all of them, especially as many FEM software are designed in a fundamentally different way.

We have a separate code measuring performance:
https://github.com/FEniCS/performance-test

[jorgensd]

@jiayingqi the results of the performance test is found at: https://fenics.github.io/performance-test-results/