Refactor rabbit_recovery_terms startup

Rename rabbit_queue_index:{recover => start}/1.
Rename rabbit_shutdown_terms{recover => start}/0.
Stop handling supervisor child-start errors explicitly.
Add {rabbit_recovery_terms, rabbit_queue_index}:stop/0 variants.
Introduce a `stop’ code path from BQ:stop/0 to qi:stop/0.
Improve recovery terms upgrade handling

Use a more specific regex to locate the old clean.dot files.
If reading an old clean.dot file fails, simply log the error.
Ensure that we close the dets table after our upgrade step has run.