Rework "hello" samples to separate starter and worker processes

Is your feature request related to a problem? Please describe.

Initially we hoped the browse-ability of having several files right next to each other like normal Python scripts showing how things are done would be worth not doing the best practice of separating starters and workers (and just adding a comment to explain).

Describe the solution you'd like

Probably need a folder per sample with separate files for starter, worker, and maybe workflows, and maybe activities. Don't need to keep under "hello" and don't have to keep separate (e.g. can combine signals and queries).

Commencez par inventorier les exemples « hello » ainsi que leurs fichiers actuels de starter, worker, workflow et activity. Définissez avec les maintainers la structure et les limites de processus prévues pour chaque exemple, puis vérifiez que chaque exemple réorganisé reste exécutable et démontre clairement le pattern prévu.