Adding missing origin to CylindricalMesh.from_domain

[shimwell]

Description

While making cylindrical meshes from a domain I noticed the mesh was not fitting the geometry correctly in the Z direction. After digging into the code I noticed that the origin was not set and therefore defaulting to 0,0,0. My geometry starts on the zplane=0 and goes upwards. Anyway this PR now sets the origin to the center of the bounding box.

Fixes # (issue)

Checklist

• I have performed a self-review of my own code
• I have run clang-format on any C++ source files (if applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)

[paulromano]

Thanks for the fix @shimwell! I realized that the documentation for z_grid was confusing in that it didn't mention that it is relative to the origin, so I just added a commit here on your branch updating that. Hope you don't mind! 😄

[shimwell]

As this is a small PR and it has been approved a few days ago I think this one can be merged