Have port destination likelihood scale with level (#1473)

## Description:

Having a high level port would increase the number of outgoing
tradeships, but not the number of incoming tradeships. Now the the
chances of a tradeship landing on a port is scaled with the port's level

## 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
- [x] I have read and accepted the CLA aggreement (only required once).

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

evan

tests/PlayerImpl.test.ts

@@ -9,6 +9,7 @@ import { setup } from "./util/Setup";
 
 let game: Game;
 let player: Player;
+let other: Player;
 
 describe("PlayerImpl", () => {
   beforeEach(async () => {
@@ -17,7 +18,10 @@ describe("PlayerImpl", () => {
       {
         instantBuild: true,
       },
-      [new PlayerInfo("player", PlayerType.Human, null, "player_id")],
+      [
+        new PlayerInfo("player", PlayerType.Human, null, "player_id"),
+        new PlayerInfo("other", PlayerType.Human, null, "other_id"),
+      ],
     );
 
     while (game.inSpawnPhase()) {
@@ -26,6 +30,7 @@ describe("PlayerImpl", () => {
 
     player = game.player("player_id");
     player.addGold(BigInt(1000000));
+    other = game.player("other_id");
 
     game.config().structureMinDist = () => 10;
   });
@@ -77,4 +82,20 @@ describe("PlayerImpl", () => {
     );
     expect(cityToUpgrade).toBe(false);
   });
+
+  test("Destination ports chances scale with level", () => {
+    game.config().proximityBonusPortsNb = () => 0;
+
+    player.conquer(game.ref(10, 10));
+    const playerPort = player.buildUnit(UnitType.Port, game.ref(10, 10), {});
+
+    other.conquer(game.ref(0, 0));
+    const otherPort = other.buildUnit(UnitType.Port, game.ref(0, 0), {});
+    otherPort.increaseLevel();
+    otherPort.increaseLevel();
+
+    const ports = player.tradingPorts(playerPort);
+
+    expect(ports.length).toBe(3);
+  });
 });