Check counting does not work for extinction pieces with extinctionPseudoRoyal = true

[SamuelTheCamel]

When extinctionPsuedoRoyal = true, the last remaining extinction piece should be treated as a royal piece, meaning it should be able to be checked. However, when checkCounting = true, the number of checks does not decrease when the last remaining extinction piece is checked. This also applies to duple checks when dupleCheck = true.

Steps to reproduce

Create a variant with the following parameters:

extinctionValue = loss
extinctionPieceTypes = (insert desired piece types here)
extinctionPseudoRoyal = true

checkCounting = true

Then, set the position such that there is only one extinction piece left for black and check it with white. Observe that the number of checks does not decrease.

Here's an example variant:

[test_extinction_check_count]

knight = n
queen = q
king = -

castling = false

extinctionValue = loss
extinctionPieceTypes = *
extinctionPseudoRoyal = true

checkCounting = true

startFen = 4n3/8/8/8/8/8/8/3Q4 w - - 9+9 0 1

Qe1 results in a check but the check counts remain as 9+9

[ianfab]

That is kind of a known limited simply because pseudoRoyal pieces are not really handled the same way as proper royal pieces, and I assumed such limitations should be fixed as part of a bigger refactoring of unifying the handling of them. However, upon checking this specific one, it seems like this could easily be addressed by just extending one single if condition at

Fairy-Stockfish/src/position.cpp

Lines 1590 to 1591 in 73b5631

	if (check_counting() && givesCheck)
	k ^= Zobrist::checks[us][st->checksRemaining[us]] ^ Zobrist::checks[us][--(st->checksRemaining[us])];

So it might actually be worth addressing this one, since it seems quite minimal.