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).

Inizia facendo un inventario degli esempi “hello” e dei relativi file attuali di starter, worker, workflow e activity. Definisci con i maintainer il layout previsto per ogni esempio e i confini dei processi, quindi verifica che ogni esempio riorganizzato sia ancora eseguibile e dimostri chiaramente il pattern previsto.