### What changes were proposed in this pull request?
This change replaces the world slave with alternatives matching the context.
### Why are the changes needed?
There is no need to call things slave, we might as well use better clearer names.
### Does this PR introduce _any_ user-facing change?
Yes, the ouput JSON does change. To allow backwards compatibility this is an additive change.
The shell scripts for starting & stopping workers are renamed, and for backwards compatibility old scripts are added to call through to the new ones while printing a deprecation message to stderr.
### How was this patch tested?
Existing tests.
Closes#28864 from holdenk/SPARK-32004-drop-references-to-slave.
Lead-authored-by: Holden Karau <hkarau@apple.com>
Co-authored-by: Holden Karau <holden@pigscanfly.ca>
Signed-off-by: Holden Karau <hkarau@apple.com>
