The last remaining double to Real changes (1/2)

All high precision code is working now. The pipeline in !366 (closed) is fully working and passes all checks and tests. I have even launched a full address sanitizer check on all high-precision types in the pipeline to be 100% sure that all is good (I start them manually one by one; but they could run in parallel with lower jobsnum ;).

So now I am writing documentation and splitting !366 (closed) into manageable and easy to verify parts. The part in this merge request is the simplest of them all: the last remaining double → Real changes. We have been doing those quite regularly in past few months. This merge request finishes these changes. There are also a couple changes MatrixXd → MatrixXr and Vector3d → Vector3r.

It is ready and can be safely merged.