Add eigentune calculation to MATRIX_Lattice

[austin-hoover]

The eigenvalues of the transfer matrix are $\lambda_k = \exp(2 \pi i \nu_k)$, where $\nu_k$ is the tune.

[austin-hoover]

This imports NumPy which is causing failed check:

  File "/__w/PyORBIT3/PyORBIT3/.po3/lib64/python3.9/site-packages/orbit/matrix_lattice/MATRIX_Lattice.py", line 12, in <module>
    import numpy as np
ModuleNotFoundError: No module named 'numpy'
    from .MATRIX_Lattice import MATRIX_Lattice
  File "/__w/PyORBIT3/PyORBIT3/.po3/lib64/python3.9/site-packages/orbit/matrix_lattice/MATRIX_Lattice.py", line 12, in <module>
    import numpy as np
ModuleNotFoundError: No module named 'numpy'
Traceback (most recent call last):
  File "/__w/PyORBIT3/PyORBIT3/examples/SpaceCharge/sc3D/read_sc_numbers.py", line 7, in <module>
    print(sizes)
NameError: name 'sizes' is not defined