Add projectile hit simulation API (#8816)

This adds API to force a projectile to hit a provided entity. Example usage could be if you have a player disguised as another entity, you could simulate an arrow colliding with the (fake) entity hitbox.

patches/api/More-Projectile-API.patch

@@ -225,6 +225,41 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +     * @param beenShot has been in shot into the world
 +     */
 +    void setHasBeenShot(boolean beenShot);
++
++    /**
++     * Gets whether this projectile can hit an entity.
++     * <p>
++     * This method returns true under the following conditions:
++     * <p>
++     * - The shooter can see the entity ({@link Player#canSee(Entity)}) <p>
++     * - The entity is alive and not a spectator <p>
++     * - The projectile has left the hitbox of the shooter ({@link #hasLeftShooter()})<p>
++     * - If this is an arrow with piercing, it has not pierced the entity already
++     *
++     * @param entity the entity to check if this projectile can hit
++     * @return true if this projectile can damage the entity, false otherwise
++     */
++    boolean canHitEntity(@org.jetbrains.annotations.NotNull Entity entity);
++
++    /**
++     * Makes this projectile hit a specific entity.
++     * This uses the current position of the projectile for the hit point.
++     * Using this method will result in {@link org.bukkit.event.entity.ProjectileHitEvent} being called.
++     * @param entity the entity to hit
++     * @see #hitEntity(Entity, org.bukkit.util.Vector)
++     * @see #canHitEntity(Entity) 
++     */
++    void hitEntity(@org.jetbrains.annotations.NotNull Entity entity);
++
++    /**
++     * Makes this projectile hit a specific entity from a specific point.
++     * Using this method will result in {@link org.bukkit.event.entity.ProjectileHitEvent} being called.
++     * @param entity the entity to hit
++     * @param vector the direction to hit from
++     * @see #hitEntity(Entity)
++     * @see #canHitEntity(Entity) 
++     */
++    void hitEntity(@org.jetbrains.annotations.NotNull Entity entity, @org.jetbrains.annotations.NotNull org.bukkit.util.Vector vector);
 +    // Paper end
  }
 diff --git a/src/main/java/org/bukkit/entity/ShulkerBullet.java b/src/main/java/org/bukkit/entity/ShulkerBullet.java