Do shallower search in case of lmr being not successful enough
In case of a move passing LMR but it results being not too far from
the current best search result produce a full depth search with reduced depth.
Original idea by lonfom169 .
Passed STC:
https://tests.stockfishchess.org/tests/view/6373409b54d69a2f33913fbd
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 169504 W: 45351 L: 44848 D: 79305
Ptnml(0-2): 598, 18853, 45353, 19344, 604
Passed LTC:
https://tests.stockfishchess.org/tests/view/6374c58528e3405283eb8d2d
LLR: 2.96 (-2.94,2.94) <0.50,2.50>
Total: 51144 W: 13802 L: 13471 D: 23871
Ptnml(0-2): 19, 4928, 15362, 5229, 34
closes https://github.com/official-stockfish/Stockfish/pull/4230
bench 4277005