Rename `qdb.lookup` so that it will not be removed

[ZiyaoLi]

The colabfold.mmseqs.search.py generates a qdb.lookup to match queries and ids. This file is useful to map back the batched results. However, this file is removed by mmseqs rmdb qdb, which basically does rm qdb*. Renaming this file avoids this (potentially accidental) removing.

[xeniorn]

This would break pairing, which relies on qdb.lookup to decide which sequences to pair. You'd need to make a copy of qdb.lookup, or rename it after the pairing part.