reduce number of trade ships by 50%, double gold per trade ship (#1934)

## Description:

v25 increased the number of trade ships from v24, causing lag
complaints. On my chromebook pathfinding is using over 60% of cpu.

So reduced the number of trade ships roughly by half, but double the
gold per trade ship so it should balance out,

World v25: 
* 2 mins: ~ 60 trade ships 
* 5 mins: ~ 140 trade ships

World on this branch:
* 2 mins: ~ 35 trade ships
* 5 mins: ~ 70 trade ships


Also increased the probably of trade ship spawn for players with under 2
tradeships to prevent larger players from starving out smaller players.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/core/execution/PortExecution.ts

@@ -79,9 +79,10 @@ export class PortExecution implements Execution {
   shouldSpawnTradeShip(): boolean {
     const numTradeShips = this.mg.unitCount(UnitType.TradeShip);
     const numPlayerPorts = this.player.unitCount(UnitType.Port);
+    const numPlayerTradeShips = this.player.unitCount(UnitType.TradeShip);
     const spawnRate = this.mg
       .config()
-      .tradeShipSpawnRate(numTradeShips, numPlayerPorts);
+      .tradeShipSpawnRate(numTradeShips, numPlayerPorts, numPlayerTradeShips);
     for (let i = 0; i < this.port!.level(); i++) {
       if (this.random.chance(spawnRate)) {
         return true;