Adds nullability annotations among other things

Adds nullability annotations for all methods
Fixes some nullability problems and inconsistencies
Gets rid of RelativeBlockVector's inner class
Changes RelativeBlockVector to a record
Simplifies FromTheEndTeleportation's storage, and makes it into a minimal record
Removes the putStringInList method
Gets rid of some primitive list usage
Fixes some incorrect method accessibility
Removes some redundancy in PortalOption

src/main/java/net/knarcraft/stargate/container/FromTheEndTeleportation.java

@@ -1,60 +1,16 @@
 package net.knarcraft.stargate.container;
 
 import net.knarcraft.stargate.portal.Portal;
-import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
 
 /**
- * This class represents a player teleporting from the end to the over-world using an artificial end portal
+ * This class represents a teleportation from the end to the over-world using an artificial end portal
  *
  * <p>This is necessary because a player entering an end portal in the end is a special case. Instead of being
  * teleported, the player is respawned. Because of this, the teleportation needs to be saved and later used to hijack
  * the position of where the player is to respawn.</p>
+ *
+ * @param exitPortal <p>The portal the player should exit from when arriving in the over-world</p>
  */
-public class FromTheEndTeleportation {
-
-    private final Player teleportingPlayer;
-    private final Portal exitPortal;
-
-    /**
-     * Instantiates a new teleportation from the end
-     *
-     * @param teleportingPlayer <p>The teleporting player</p>
-     * @param exitPortal        <p>The portal to exit from</p>
-     */
-    public FromTheEndTeleportation(Player teleportingPlayer, Portal exitPortal) {
-        this.teleportingPlayer = teleportingPlayer;
-        this.exitPortal = exitPortal;
-    }
-
-    /**
-     * Gets the teleporting player
-     *
-     * @return <p>The teleporting player</p>
-     */
-    public Player getPlayer() {
-        return this.teleportingPlayer;
-    }
-
-    /**
-     * Gets the portal to exit from
-     *
-     * @return <p>The portal to exit from</p>
-     */
-    public Portal getExit() {
-        return this.exitPortal;
-    }
-
-    @Override
-    public int hashCode() {
-        return teleportingPlayer.hashCode();
-    }
-
-    @Override
-    public boolean equals(Object other) {
-        if (!(other instanceof FromTheEndTeleportation otherTeleportation)) {
-            return false;
-        }
-        return teleportingPlayer.equals(otherTeleportation.teleportingPlayer);
-    }
-
+public record FromTheEndTeleportation(@NotNull Portal exitPortal) {
 }