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/utility/MaterialHelper.java

@@ -2,6 +2,7 @@ package net.knarcraft.stargate.utility;
 
 import org.bukkit.Material;
 import org.bukkit.Tag;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * This class helps decide properties of materials not already present in the Spigot API
@@ -18,7 +19,7 @@ public final class MaterialHelper {
      * @param material <p>The material to check</p>
      * @return <p>True if the material is a wall coral</p>
      */
-    public static boolean isWallCoral(Material material) {
+    public static boolean isWallCoral(@NotNull Material material) {
         //Unfortunately, there is no tag for dead wall corals, so they need to be checked manually
         return Tag.WALL_CORALS.isTagged(material) ||
                 material.equals(Material.DEAD_BRAIN_CORAL_WALL_FAN) ||
@@ -34,7 +35,7 @@ public final class MaterialHelper {
      * @param material <p>The material to check</p>
      * @return <p>True if the material is a container</p>
      */
-    public static boolean isContainer(Material material) {
+    public static boolean isContainer(@NotNull Material material) {
         return Tag.SHULKER_BOXES.isTagged(material) || material == Material.CHEST ||
                 material == Material.TRAPPED_CHEST || material == Material.ENDER_CHEST;
     }
@@ -45,7 +46,7 @@ public final class MaterialHelper {
      * @param material <p>The material to check</p>
      * @return <p>True if the material can be used as a button</p>
      */
-    public static boolean isButtonCompatible(Material material) {
+    public static boolean isButtonCompatible(@NotNull Material material) {
         return Tag.BUTTONS.isTagged(material) || isWallCoral(material) || isContainer(material);
     }