Verbose logging of delta-files compaction

For checkpoints we have a very extensive log message, that shows the duration of each checkpoint's phase. We don't have that for compactor.

In this Jira we need to implement that. The list of phases and statistics is at developers discretion.

As a bonus, we might want to print some values in microseconds instead of milliseconds, and not use fast timestamp (they don't have enough granularity). While we're doing that for compactor logs, we might as well update checkpoint's logs.