Index selection strategy for reindexing based on relative bloat levels

We currently choose indexes for reindexing by absolute bloat level (highest bloat first). We're now in a situation where we're repeatedly reindexing the same indexes, although their relative bloat is not high really.

Proposed change: Select indexes by relative bloat level (bloat estimate / index size) and only after having crossed a configurable threshold (start with 10%).

Definition of Done

1. Reindexing orders indexes by relative bloat levels instead of absolute bloat levels
2. Reindexing excludes indexes below a configurable threshold (10%) for relative bloat