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).

首先盘点“hello”示例及其当前的 starter、worker、workflow 和 activity 文件。与维护者一起定义每个示例预期的布局和进程边界，然后验证每个重新组织后的示例仍然可以运行，并且清晰地展示其预期模式。