Turning a coordinate or object to a coordinate (i.e. make _pointify publicly available)

Nobody has claimed this yet.

## Description of proposed feature

In some libraries I don’t want to consider whether the user gives a coordinate or a mobject as input. For instance, to compute the barycenter between two points or objects (it’s also weird to see that no such native function exists in Manim.

I’d therefore love to have:
- a function to convert a point/object to coordinate, like:
```
def to_point(mob_or_point, direction=None):
if isinstance(mob_or_point, (Mobject, OpenGLMobject)):
mob = mob_or_point
if direction is None:
return mob.get_center()
else:
return mob.get_boundary_point(direction)
return np.array(mob_or_point)
```
- a function to compute the barycenter between two objects, like:
```
def barycenter(obj1, obj2, alpha=1/2): ## Ideally: also work for a set of points, where alpha is a list of size n-1
return (1-alpha)*to_point(obj1) + alpha*to_point(obj2)
```
It could for instance improve the midpoint function (https://docs.manim.community/en/stable/_modules/manim/utils/space_ops.html#midpoint) to work on arbitrary objects with a parameter alpha.

## How can the new feature be used?

In many ways. For instance to define animations where we need to place points depending on other points.

Start by reading the existing midpoint implementation in manim/utils/space_ops.py and locate the internal _pointify behavior referenced by the issue. Determine how coordinate and Mobject inputs, optional directions, and barycenter interpolation should be covered; done means the agreed public API works for the described inputs with corresponding tests.

Written by the indexing model from the issue text.