Mpcd Cosine and CosineExpansionContraction Channels

[baho-cb]

Description

This PR adds two new mpcd streaming geometries: Serpentine channel (CosineChannel) and sinusoidal expansion and contraction channel (CosineExpansionContraction).

~This PR should be merged after the rejection filler PR (#1822).~ This PR has been merged.

Motivation and context

Resolves #1775, #1776

How has this been tested?

Python tests are added for the geometries and streaming.

Change log

* `mpcd.geometry.CosineChannel` for a serpentine (cosine) channel.
* `mpcd.geometry.CosineExpansionContraction` for an expansion-contraction channel.

Checklist:

• [x] I have reviewed the Contributor Guidelines.
• [x] I agree with the terms of the HOOMD-blue Contributor Agreement.
• [x] My name is on the list of contributors (sphinx-doc/credits.rst) in the pull request source branch.