chore(nx-plugin): add floating promises lint rules in order to catch nasty bugs

[Hotell]

• migrate all generator tempaltes to have .template extension which is stripped away by nx devkit
  • this also makes tooling setup more easier as otherwise these templates are consumed by eslint/tsc etc which is wrong
• introduces crucial Promise related lint rules for nx-plugin project
  • "@typescript-eslint/await-thenable": "error",
  • "@typescript-eslint/no-misused-promises": "error",
  • "@typescript-eslint/no-floating-promises": "error"
• fixes exposed critical runtime issue in one of ours executors