Align and collapse shared NNUE mappings
Make the existing MADV_HUGEPAGE request effective for the Linux shared NNUE
mapping.
Map large shared objects at a 2 MiB-aligned address and request MADV_COLLAPSE
after the creating process initializes the network.
pyshbench, 30 runs:
```text
Platform / target Speedup 95% CI
Graviton 3 / armv8-dotprod +2.675% [+2.495%, +2.856%]
AMD Zen 3 / x86-64-bmi2 +0.479% [+0.182%, +0.776%]
Intel Sapphire / x86-64-avx512icl +2.073% [+1.675%, +2.470%]
```
STC passed:
```text
LLR: 2.96 (-2.94,2.94) <0.00,2.00>
Total: 37344 W: 9716 L: 9419 D: 18209
Ptnml(0-2): 54, 3890, 10497, 4167, 64
```
https://tests.stockfishchess.org/tests/view/6a80cc2adb2c105c37ecd9cf
closes https://github.com/official-stockfish/Stockfish/pull/7058
No functional change