IPVGO: Support scripts playing against each other as each color on "No AI" boards (#1917)

This is a big change with a *lot* of moving parts.

The largest part of it is enabling scripts to `playAsWhite` as a parameter to many Go functions. In the implementation, this involved a significant rewrite of `opponentNextTurn` promise handling.

A number of other changes and bugfixes are included:
* Fixes the issue where handicap stones are added on game load.
* Better typing for error callbacks.
* Throw errors instead of deadlocking on bad cheat usage.
* Return always-resolved gameOver promise after game end
* Added a new `resetStats` api function.

---------

Co-authored-by: David Walker <d0sboots@gmail.com>

src/Go/boardState/boardState.ts

@@ -34,6 +34,7 @@ export function getNewBoardState(
     ai: ai,
     passCount: 0,
     cheatCount: 0,
+    cheatCountForWhite: 0,
     board: Array.from({ length: boardSize }, (_, x) =>
       Array.from({ length: boardSize }, (_, y) =>
         !boardToCopy || boardToCopy?.[x]?.[y]
@@ -151,7 +152,18 @@ export function passTurn(boardState: BoardState, player: GoColor, allowEndGame =
  * Modifies the board in place.
  */
 export function applyHandicap(board: Board, handicap: number): void {
-  const availableMoves = getEmptySpaces(board);
+  const availableMoves = [];
+  for (const column of board) {
+    for (const point of column) {
+      if (point) {
+        if (point.color !== GoColor.empty) {
+          // Game is in progress, don't apply handicap
+          return;
+        }
+        availableMoves.push(point);
+      }
+    }
+  }
   const handicapMoveOptions = getExpansionMoveArray(board, availableMoves);
   const handicapMoves: Move[] = [];