upgrade unit when building a unit of same type (#1328)

## Description:

When building a structure in the same location as a nearby structure, it
will update the existing structure instead of creating a new one.

Also fix ctrl+click shortcut to bring up the build menu.

## 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 understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

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

evan

src/client/graphics/layers/PlayerActionHandler.ts

@@ -1,14 +1,8 @@
 import { EventBus } from "../../../core/EventBus";
-import {
-  Cell,
-  PlayerActions,
-  PlayerID,
-  UnitType,
-} from "../../../core/game/Game";
+import { Cell, PlayerActions, PlayerID } from "../../../core/game/Game";
 import { TileRef } from "../../../core/game/GameMap";
 import { PlayerView } from "../../../core/game/GameView";
 import {
-  BuildUnitIntentEvent,
   SendAllianceRequestIntentEvent,
   SendAttackIntentEvent,
   SendBoatAttackIntentEvent,
@@ -67,13 +61,6 @@ export class PlayerActionHandler {
   ): Promise<TileRef | false> {
     return await player.bestTransportShipSpawn(tile);
   }
-
-  handleBuildUnit(unitType: UnitType, cellX: number, cellY: number) {
-    this.eventBus.emit(
-      new BuildUnitIntentEvent(unitType, new Cell(cellX, cellY)),
-    );
-  }
-
   handleSpawn(spawnCell: Cell) {
     this.eventBus.emit(new SendSpawnIntentEvent(spawnCell));
   }