dx: CI & demo must be one-click runnable

[pepyakin]

The CI is the last line of defence. It may take quite some wall time, because it may afford to be very thorough. However, it's probably a bad DX (Developer Experience) to rely on it when developing stuff. You don't want to wait 10-30 minutes only to see some compilation error. In the most cases, it's enough to just run superficial tests to uncover the vast majority of errors.

It's essential to do be able to do this quickly. However, atm, it's rather annoying. The repo already hosts several projects and it will host more (#86 or more adapters with their tests). At the same time, the DX of running them is subpar.

Ideally, those workflows should be runnable with a single command. Maybe, something like cargo xtask idiom may help. To enforce reliability, ideally, the same command should serve the CI. This way we can make sure that the workflow always work as expected.