Allow pruning at PV nodes in QS

And correspondingly remove NodeType from
qsearch template parameters.

Tested in no-regression mode.

Passed STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 27555 W: 5832 L: 5722 D: 16001

And LTC
LLR: 6.55 (-2.94,2.94) [-3.00,1.00]
Total: 107424 W: 19010 L: 18844 D: 69570

bench: 7798244