[Take 2] Implement Jax-compatible PauliString

Created by: PhilipVinc

This is also a remanding of the original PR by @wdphy16 , following the new infrastructure for Jax-compatible operators.

resuscitates #968

@wdphy16 as you are the original author of the code, could you please go back through it and comment it throughout? It's very complicated and it's very hard to follow what the generation of masks do...

To merge it we should document it so that in the future other people can maintain it as well.