feat: expose runner APIs for running individual steps

[OrKoN]

The idea behind this PR is to make the code we generate more composable: instead of providing the entire recording one can run individual steps either using .runStep method or more specific .click etc. methods and, for example, easily integrate it into control flow statements. As the next item, we could also change the createRunner API to make the flow optional.

BREAKING CHANGE: the user flow parameter in the runner extensions is now optional