Document CDS support

[philwebb]

With the Antora migration mostly done we might want to add some more documentation around CDS

[mhalbritter]

We're using the CDS friendly layout in our "Dockerfiles" doc by default now (see #40094).

[mhalbritter]

I've updated the "Efficient deployments" section.

[mhalbritter]

There are some bits missing. We could link to the Spring Framework docs. And we could explain the CDS workflow: first, start the training run, then use the classes archive.

[mhalbritter]

Fixed by #40175.