QueryMatcher fix and some small aux data related fixes

[mvankem]

1. QueryMatcher: rescore truncated-score diagonals when the buffer is too full for radix sort

This change improves prefilter sensitivity for queries that produce many diagonal hits. When there are more diagonals with truncated ungapped scores (score == 255) than max-seqs, we need to rescore them to break ties meaningfully. Previously, rescoring + radix sort was only performed when all diagonal hits fit into the double-buffer — both the truncated ones and the ones with scores below 255. When they did not fit, we fell back to a serial sort, and ties between truncated scores were broken arbitrarily without rescoring.

The fix first filters out all diagonals with scores below the final diagonalThr — those are not going to be considered anyway. Rescoring + radix sort is then performed only on the truncated-score subset, which typically fits into the buffer.

2. Add --aux-score flag — Lets the user disable the use of aux seqs in the prefilter.

3. Fix prefiltering query without aux data against targets with aux data — Corrects the aux-data handling when only one side of the search provides aux sequences.

[mvankem]

@martin-steinegger this changes the prefiltering, you might want to have a look