VVLTC search tune

Parameters were tuned in 3 stages:

* Using an earlier L1-3072 net, and with triple extension margin manually set to 0: https://tests.stockfishchess.org/tests/view/65ffdf5d0ec64f0526c544f2 (~30k games)
* Continue tuning, but with the previous master net (L1-2560). https://tests.stockfishchess.org/tests/view/660663f00ec64f0526c59c41 (~27k games)
* Starting with the parameters from step 2, use the current L1-3072 net, and allow the triple extension margin to be tuned starting from 0: https://tests.stockfishchess.org/tests/view/660c16b8216a13d9498e7536 (40k games)

Passed VVLTC 1st sprt: https://tests.stockfishchess.org/tests/view/66115eacbfeb43334bf7eddd
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 27138 W: 7045 L: 6789 D: 13304
Ptnml(0-2): 1, 2421, 8471, 2673, 3

Passed VVLTC 2nd sprt: https://tests.stockfishchess.org/tests/view/661483623eb00c8ccc0049c1
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 26242 W: 6807 L: 6535 D: 12900
Ptnml(0-2): 0, 2353, 8143, 2625, 0

STC Elo estimate: https://tests.stockfishchess.org/tests/view/66175ca55a4693796d96608c
Elo: -10.53 ± 2.4 (95%) LOS: 0.0%
Total: 21584 W: 5294 L: 5948 D: 10342
Ptnml(0-2): 102, 2937, 5363, 2293, 97
nElo: -19.99 ± 4.7 (95%) PairsRatio: 0.79

closes https://github.com/official-stockfish/Stockfish/pull/5162

Bench: 1381387

src/evaluate.h

@@ -29,7 +29,7 @@ class Position;
 
 namespace Eval {
 
-constexpr inline int SmallNetThreshold = 1165, PsqtOnlyThreshold = 2500;
+constexpr inline int SmallNetThreshold = 1274, PsqtOnlyThreshold = 2389;
 
 // The default net name MUST follow the format nn-[SHA256 first 12 digits].nnue
 // for the build process (profile-build and fishtest) to work. Do not change the