added parallelization to the actual cross-checking part of Crosscheck…

[yfarjoun]

Summary

Parallelizes fingerprint comparisons using the existing NUM_THREADS parameter.

Previously, while fingerprint loading used multiple threads, the actual comparisons were performed sequentially. This PR adds parallelization to the two comparison methods:

• crossCheckFingerprints() - pairwise comparison of all fingerprint groups
• checkFingerprintsBySample() - sample-by-sample comparison when using SECOND_INPUT

Changes

• A few thread-safety changes
• Modified crossCheckFingerprints() to use a parallel IntStream over row indices with a custom ForkJoinPool(NUM_THREADS)
• Modified checkFingerprintsBySample() to use parallelStream() with a custom ForkJoinPool(NUM_THREADS)

Notes

• The NUM_THREADS parameter now controls both fingerprint loading and comparisons
• The matrix output (crosscheckMatrix) is safe without synchronization since each cell is written by exactly one (row, col) pair
• Removed per-comparison progress logging since it's not meaningful with parallel execution; replaced with a single log message at the start showing total comparisons and
  thread count

Test plan

• Existing CrosscheckFingerprintsTest tests pass
• Verify parallel execution with NUM_THREADS > 1 produces identical results to single-threaded