Shelter safety by pawns, storm and blocked storm (sfc style)

[TheRealGioviok]

Differently from sfc, we keep separate tapered values. Doing either of the smaller component alone didn't gain.

Passed STC

Test  | shelter_impl
Elo   | 3.84 +- 2.60 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=16MB
LLR   | 2.95 (-2.94, 2.94) [0.00, 3.00]
Games | N: 23340 W: 5927 L: 5669 D: 11744
Penta | [258, 2765, 5418, 2919, 310]

https://clockworkopenbench.pythonanywhere.com/test/1105/

Passed LTC

Test  | shelter_impl
Elo   | 4.91 +- 2.94 (95%)
SPRT  | 40.0+0.40s Threads=1 Hash=64MB
LLR   | 2.96 (-2.94, 2.94) [0.00, 3.00]
Games | N: 15768 W: 3837 L: 3614 D: 8317
Penta | [82, 1846, 3843, 1993, 120]

https://clockworkopenbench.pythonanywhere.com/test/1106/

Bench: 14058851