Spring Rename class-data-sharing.html to cds.html

Project Leyden is likely going to change the meaning of CDS from Class Data Sharing to Cache Data Store, see the related new workflow documentation for more details.

In order to be future proof, https://docs.spring.io/spring-framework/reference/integration/class-data-sharing.html should be named to cds.html (with the old link redirected to the new one).