Add ECAdd() Bloq

[fpapa250]

Adds ECAdd bloq with classical simulation. I broke the bloq into the 6 steps shown in https://arxiv.org/abs/2306.08585. I classically simulated all steps. I put in a shimmed ModInv classical implementation (it's not montgomery mod inversion, but it still works on ECPoints not in montgomery form; I'm a little stuck on understanding what to do for R in montgomery mod inversion).

[fpapa250]

Dependent on https://github.com/quantumlib/Qualtran/pull/1424. For testing purposes I put the bug fix in this branch too, but it should be merged first.