Add logging of attempts and return status

Hi.

It would be nice if one could observe what retry actually does, ie. to have it report a command's return code when it failed, how many attempts are left, timings of the command runs, how much time it is going to sleep until the next attempt et cetera.

Thank you!

No file, test, or entry point is named in the issue, so first locate where retry attempts, command return codes, and sleep intervals are handled. Define the logging output and timing behavior for failures, remaining attempts, command runs, and waits; done means those events are observable during retries.

Written by the indexing model from the issue text.