`CalcBoundingBox` for `geometry::Shape` types

[dmcconachie-tri]

Is your feature request related to a problem? Please describe.
I am creating approximate bounding boxes for rigid bodies made up of arbitrary shapes; in order to achieve this I need to get the bounding boxes of each component shape that makes up the rigid body.

Describe the solution you'd like
A virtual function in drake::geometry::Shape which is then implemented in each concrete Shape type.

Describe alternatives you've considered
A else if tree of dynamic_casts is functional but poor design.

Additional context
Some of the Shape types will have additional challenges regarding the implementation of such a function, in particular HalfSpace, Convex. and Mesh. For my particular application I don't need these solved, though they could be solved at the same time.

[jwnimmer-tri]

A virtual function in drake::geometry::Shape which is then implemented in each concrete Shape type.

Another (probably better) option is a namespace function that returns the answer. One current example of this design is the function

double drake::geometry::CalcVolume(const Shape& shape);

[rpoyner-tri]

Related: #15121