Reorganize workflow related commands in the debusine command line interface

We should restructure the commands related to workflows available in the debusine CLI to match the new vocabulary defined in #868 (closed). We probably also want to adopt a structure similar to the one used for debusine-admin where you have debusine-admin <object-type> <action>.

We could have a command line that goes like this:

• debusine workflow-template create (or debusine workflow configure? or debusine workflow define?) (instead of debusine create-workflow-template) ( !2287 (merged), !2339 (merged))
• debusine workflow-template edit (#767 (closed), lowered to P2)
• debusine workflow-template manage (!2343 (merged))
• debusine workflow start (instead of debusine create-workflow) (!2314 (merged))
• debusine workflow abort (in addition to debusine work-request abort) (#1117 (backlogged))
• debusine workflow list (#861, backlogged)

(split off #770 (closed), /cc @mbehrle)