Add bulk off-heap scoring for uint8 quantized vectors using Panama Vector API

Adds 4-wide bulk dot product and square distance operations for uint8
quantized vectors using the Panama Vector API with MemorySegment-based
data access. This reduces reduceLanes calls by 4x compared to single-
vector scoring, which helps under icache pressure during HNSW graph
traversal.

Key implementation details:
- Uint8DotProduct and Uint8SqrDistance inner classes in
  MemorySegmentBulkVectorOps with platform-specific widening:
  - 128-bit: bytes -> shorts -> ints (2 convertShape parts)
  - 256-bit: bytes -> ints directly
  - 512-bit: bytes -> shorts -> ints (single part)
- UINT8_NEEDS_PART1 guard prevents convertShape(..., 1) call on 512-bit
  where all 16 shorts fit in 16 ints in a single part
- Int4 bulk scoring is explicitly not implemented; int4 scorers fall
  back to the existing single-vector Panama/Native paths via !isUint8()
  guard in bulkScoreBody

Tests cover: basic uint8 (int7), large dimensions (128), odd dimensions
(97), SIMD boundaries (15/16/17), tail paths (0-3 nodes), updateable
scorer (MemorySegment query), and int4 fallback verification.

Benchmarks (AMD Ryzen 7 7800X3D, AVX-512):
- Float32 bulk: ~1.5x speedup (reference)
- Uint8 bulk (clean icache): ~5-7% regression
- Uint8 bulk (polluted icache): ~2x speedup

Int4 bulk was evaluated but benchmarked ~2.3x slower than single-vector
and has been removed from this PR.

Author: iprithv

lucene/CHANGES.txt

@@ -385,6 +385,8 @@ Improvements
 
 Optimizations
 ---------------------
+* GITHUB#16203: Add bulk off-heap scoring for uint8 quantized vectors using Panama Vector API. (Prithvi S)
+
 * GITHUB#16176: Restore WANDScorer for TOP_SCORES + minShouldMatch > 1. (Tianxiao Wei)
 
 * GITHUB#16153: Use TernaryLongHeap in UpdateGraphsUtils for faster HNSW graph merging. (Prithvi S)