Implement Compton scattering as a new binary process

[RemiLehe]

It might be useful to have the ability to compute scattering between electron macroparticles and photon macroparticles.

Note that we could reuse parts of the FBPIC implementation (which itself is based on an earlier implementation in Warp): https://github.com/fbpic/fbpic/blob/dev/fbpic/particles/elementary_process/compton/inline_functions.py#L43 (The implementation in FBPIC is for scattering between electron macroparticles and a background density of photons - instead of photon macroparticles. However, the above probability function could be reused for binary collisions between macroparticles.)

We could also reuse this test case for automated testing: https://github.com/fbpic/fbpic/blob/dev/tests/test_compton.py

[RemiLehe]

@lucafedeli88 pointed out that this process is implemented in:

• CALDER (see https://indico.ijclab.in2p3.fr/event/8018/contributions/25315/attachments/18864/25444/Workshop_GDR_APPEL22_Gremillet_v3.pdf and https://theses.hal.science/tel-03653070)
• Osiris (see https://ui.adsabs.harvard.edu/abs/2017APS..DPPB11030D/abstract, [https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/compton-sca[…]ing-in-particleincell-codes/4A2BE5F3AB821F6B7D45E36CC0FBB48F](https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/compton-scattering-in-particleincell-codes/4A2BE5F3AB821F6B7D45E36CC0FBB48F, https://arxiv.org/abs/2003.04249)

[RemiLehe]

Another useful reference: https://journals.aps.org/prab/pdf/10.1103/PhysRevAccelBeams.25.084601