Update default main net to nn-e8bac1c07a5a.nnue

Created by modifying L2 weights from the previous main net (nn-74f1d263ae9a.nnue)
with params found by spsa around 9k / 120k games at 120+1.2.

370 spsa params - L2 weights in nn-74f1d263ae9a.nnue where |val| >= 50
A: 6000, alpha: 0.602, gamma: 0.101
weights: [-127, 127], c_end = 6

To print the spsa params with nnue-pytorch:
```
import features
from serialize import NNUEReader

feature_set = features.get_feature_set_from_name("HalfKAv2_hm")
with open("nn-74f1d263ae9a.nnue", "rb") as f:
    model = NNUEReader(f, feature_set).model

c_end = 6
for i in range(8):
    for j in range(32):
        for k in range(30):
            value = int(model.layer_stacks.l2.weight[32 * i + j, k] * 64)
            if abs(value) >= 50:
                print(f"twoW[{i}][{j}][{k}],{value},-127,127,{c_end},0.0020")
```

Among the 370 params, 229 weights were changed.
  avg change: 0.0961 ± 1.67
  range: [-4, 3]

The number of weights changed, grouped by layer stack index,
shows more weights were modified in the lower piece count buckets:
[54, 52, 29, 23, 22, 18, 14, 17]

Found with the same method described in:
https://github.com/official-stockfish/Stockfish/pull/5459

Passed STC:
https://tests.stockfishchess.org/tests/view/668aec9a58083e5fd88239e7
LLR: 3.00 (-2.94,2.94) <0.00,2.00>
Total: 52384 W: 13569 L: 13226 D: 25589
Ptnml(0-2): 127, 6141, 13335, 6440, 149

Passed LTC:
https://tests.stockfishchess.org/tests/view/668af50658083e5fd8823a0b
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 46974 W: 12006 L: 11668 D: 23300
Ptnml(0-2): 25, 4992, 13121, 5318, 31

closes https://github.com/official-stockfish/Stockfish/pull/5466

bench 1300471

src/evaluate.h

@@ -33,7 +33,7 @@ namespace Eval {
 // for the build process (profile-build and fishtest) to work. Do not change the
 // name of the macro or the location where this macro is defined, as it is used
 // in the Makefile/Fishtest.
-#define EvalFileDefaultNameBig "nn-74f1d263ae9a.nnue"
+#define EvalFileDefaultNameBig "nn-e8bac1c07a5a.nnue"
 #define EvalFileDefaultNameSmall "nn-37f18f62d772.nnue"
 
 namespace NNUE {