Add SMP Support

[jw1912]

• Redoes the LRU system to be usable with multiple threads
  • it is unfortunately not possible to be so uncompromising with a threading friendly LRU system, hence the new system leads to a lower effective tree size and hence actually an elo loss when single-threaded at lower hash sizes
• Adds SMP, using virtual loss

Passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,4.00>
Total: 2416 W: 682 L: 523 D: 1211
Ptnml(0-2): 20, 241, 553, 348, 46
https://montychess.org/tests/view/66afc81a0f6f1e65cfa2b2a8

Passed LTC:
LLR: 2.94 (-2.94,2.94) <1.00,5.00>
Total: 3900 W: 986 L: 825 D: 2089
Ptnml(0-2): 20, 422, 930, 533, 45
https://montychess.org/tests/view/66afea690f6f1e65cfa2b388

Thread Scaling w/ 2x Hash:
Elo: 87.16 ± 10.9 (95%) LOS: 100.0%
Total: 1404 W: 506 L: 161 D: 737
Ptnml(0-2): 4, 66, 272, 301, 59
nElo: 150.89 ± 20.7 (95%) PairsRatio: 5.14
https://montychess.org/tests/view/66afedb00f6f1e65cfa2b3a9

Thread Scaling w/ Default Hash:
Elo: 48.76 ± 16.5 (95%) LOS: 100.0%
Total: 624 W: 200 L: 113 D: 311
Ptnml(0-2): 3, 51, 133, 106, 19
nElo: 81.44 ± 28.1 (95%) PairsRatio: 2.31
https://montychess.org/tests/view/66afa71a0f6f1e65cfa2b272

Bench: 1954267