Generate default names for Workers processes

https://redmine.teklia.com/issues/9047

Calling Process.run() on a Workers process when there are no existing runs (aka starting a process) should automatically set Process.name if it wasn't already.

The default process name is a concatenation of every worker name, ordered by depth then name. When the same worker is found multiple times with the same depth, it is not repeated. When the same worker is found multiple times with different depths, it is repeated. Initialisation workers should be ignored.

For example, with this configuration:

graph LR
init_elements --> A1[A]
init_elements --> A2[A]
A1 --> B1[B]
A2 --> C
C --> B2[B]

The default process name would be A, B, C, B.

Process.name cannot exceed 250 characters, so a name that gets excessively long should be trimmed with a … at the end.