Add JMH benchmarks comparing read I/O strategies under memory pressure

[neoremind]

Adds JMH benchmarks to compare read I/O strategies in memory constrained scenario, related to #16044.

I/O strategies tested:

• mmap no madvise
• mmap + MADV_NORMAL + MADV_WILLNEED
• mmap + MADV_RANDOM
• mmap + MADV_RANDOM + MADV_WILLNEED
• FFI pread(2) via Panama
• FileChannel + DirectByteBuffer (simulates NIOFSDirectory)
• FileChannel + HeapByteBuffer
• O_DIRECT

Thread counts: 1, 4, 8, 16.

How to run

dd if=/dev/urandom of=/path/to/pread-bench-16G.dat bs=1M count=16384

java -jar lucene/benchmark-jmh/build/benchmarks/lucene-benchmark-jmh-11.0.0-SNAPSHOT.jar RandomReadIOBenchmark \
  -jvmArgs "--enable-native-access=ALL-UNNAMED -Xms2g -Xmx2g -Dbench.file=/path/to/pread-bench-16G.dat -Dbench.fileSizeMB=16384" \
  -p readSize=16384 -p readsPerOp=16