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).

まず「hello」サンプルと、現在の starter、worker、workflow、activity ファイルを一覧化します。各サンプルで意図するレイアウトとプロセス境界をメンテナーと定義し、その後、再編成した各サンプルが引き続き実行可能で、意図したパターンを明確に示していることを確認します。