fix(core): prevent bots from invading/attacking themselves (#3865) (#4014)

Resolves #4094

## Description:

In Free-For-All (FFA) mode where teams default to 0, player isOnSameTeam
checks returned false for oneself, allowing players to attack
themselves. Consequently, if a bot conquered the targeted tile between
queueing a transport ship action and its actual initialization, the
target became itself, causing the bot to execute a self-invasion.

This fix adds a reflexive check in PlayerImpl.ts's isFriendly method to
always treat oneself as friendly. It also adds a safety guard in
TransportShipExecution.ts's init method to abort ship execution if the
target has shifted to the attacker.

## 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:

barfires

src/core/execution/TransportShipExecution.ts

@@ -91,6 +91,11 @@ export class TransportShipExecution implements Execution {
       }
     }
 
+    if (this.target === this.attacker) {
+      this.active = false;
+      return;
+    }
+
     if (this.target.isPlayer() && !this.attacker.canAttackPlayer(this.target)) {
       this.active = false;
       return;