Implement UCI go nodes and go searchmoves

[binarylab2022-del]

Objective

Extend the UCI host so that it correctly enforces the go nodes and
go searchmoves command parameters.

Expected work

• parse nodes and searchmoves;
• apply a hard node limit during iterative deepening;
• restrict root move generation when searchmoves is supplied;
• preserve compatibility with the existing time and depth limits;
• add UCI regression tests;
• document the supported behavior.

Acceptance criteria

• go nodes N stops after respecting the configured node budget;
• go searchmoves ... searches only the supplied legal root moves;
• invalid or illegal moves are handled safely;
• existing UCI smoke tests remain green.