Move examples from sage.geometry.riemannian_manifolds to sage.manifolds #32228
Description
... with deprecation
Depends on #32116
Depends on #32102
CC: @egourgoulhon @mjungmath @videlec
Component: manifolds
Author: Matthias Koeppe
Branch/Commit: u/mkoeppe/move_examples_from_sage_geometry_riemannian_manifolds_to_sage_manifolds @ 1b4fe44
Issue created by migration from https://trac.sagemath.org/ticket/32228