Create center of rotation calculation

There are two potential parts to this: a function to calculate the displacement based on the inputs, and maybe a plan that does the whole process given a delta_phi. The issue with the plan may be how to find an optimal position when the profile is not easy to adjust to a slit or peak function.

No file, test, or entry point is named in the issue. Start by locating the existing profile and plan code, then clarify the expected displacement calculation and whether the delta_phi workflow should be included; done means the scope and behavior are defined well enough to test.

Written by the indexing model from the issue text.