housekeeping: Always log repository info in `OptimizeRepository`

When optimizing repositories via housekeeping.OptimizeRepository, then we only log repository information when we actually repack objects. Furthermore, we derive the repository information twice in that case: once to inform the optimization strategy, and once to log the information when repacking objects.

This MR simplifies the way we derive information in the heuristical optimization strategy by just embeding a stats.RepositoryInfo structure directly. This allows us to easily always log the repository information and deduplicates deriving the information.