Add `fvtt package repair` functionality

[rikmarais]

Database corruption can be next to impossible to fix for the end user, leaving users who are unfortunate enough to experience it with no recourse.

Foundry CLI can allow the user to leverage the ClassicLevel repair method, which can fix instances of LevelDB corruption. That method also performs database compaction.

See classic-level documentation. Some data may be lost, but this may be preferable to being unable to open the database entirely.