Pcvl 791 add symmetric mzi and improve generic interferometer

[MarionQuandela]

No description provided.

[MarionQuandela]

Script to test this branch:

import perceval as pcvl

mzi_generator_func = pcvl.catalog['symmetric mzi'].generate
def upper_component_gen(idx: int):
    return pcvl.PS(phi=pcvl.Parameter(f"φ_upper_{idx}"))
def lower_component_gen(idx: int):
    return pcvl.PS(phi=pcvl.Parameter(f"φ_lower_{idx}"))

c = pcvl.GenericInterferometer(6, mzi_generator_func,
                               upper_component_gen=upper_component_gen, lower_component_gen=lower_component_gen)
pcvl.pdisplay(c)