Add entity knockback events

- EntityKnockbackEvent
- EntityPushedByEntityAttackEvent
- EntityKnockbackByEntityEvent

Co-authored-by: aerulion <aerulion@gmail.com>
Co-authored-by: Jake Potrebic <jake.m.potrebic@gmail.com>

paper-server/patches/sources/net/minecraft/world/entity/projectile/AbstractArrow.java.patch

@@ -49,7 +49,7 @@
 +        // CraftBukkit start - handle the owner before the rest of things
 +        this(type, x, y, z, world, stack, weapon, null);
 +    }
- 
++
 +    protected AbstractArrow(EntityType<? extends AbstractArrow> entitytypes, double d0, double d1, double d2, Level world, ItemStack itemstack, @Nullable ItemStack itemstack1, @Nullable LivingEntity ownerEntity) {
 +        this(entitytypes, world);
 +        this.setOwner(ownerEntity);
@@ -57,7 +57,7 @@
 +        this.pickupItemStack = itemstack.copy();
 +        this.setCustomName((Component) itemstack.get(DataComponents.CUSTOM_NAME));
 +        Unit unit = (Unit) itemstack.remove(DataComponents.INTANGIBLE_PROJECTILE);
-+
+ 
          if (unit != null) {
              this.pickup = AbstractArrow.Pickup.CREATIVE_ONLY;
          }
@@ -118,6 +118,18 @@
          }
  
      }
+@@ -386,9 +410,9 @@
+     }
+ 
+     @Override
+-    public void push(double deltaX, double deltaY, double deltaZ) {
++    public void push(double deltaX, double deltaY, double deltaZ, @Nullable Entity pushingEntity) { // Paper - add push source entity param
+         if (!this.isInGround()) {
+-            super.push(deltaX, deltaY, deltaZ);
++            super.push(deltaX, deltaY, deltaZ, pushingEntity); // Paper - add push source entity param
+         }
+     }
+ 
 @@ -423,7 +447,7 @@
              }
  
@@ -160,6 +172,15 @@
                  }
              }
          }
+@@ -538,7 +568,7 @@
+             Vec3 vec3d = this.getDeltaMovement().multiply(1.0D, 0.0D, 1.0D).normalize().scale(d0 * 0.6D * d1);
+ 
+             if (vec3d.lengthSqr() > 0.0D) {
+-                target.push(vec3d.x, 0.1D, vec3d.z);
++                target.push(vec3d.x, 0.1D, vec3d.z, this); // Paper - Add EntityKnockbackByEntityEvent and EntityPushedByEntityAttackEvent
+             }
+         }
+ 
 @@ -675,7 +705,7 @@
          }
  

paper-server/patches/sources/net/minecraft/world/entity/projectile/windcharge/AbstractWindCharge.java.patch

@@ -10,6 +10,15 @@
  
  public abstract class AbstractWindCharge extends AbstractHurtingProjectile implements ItemSupplier {
  
+@@ -98,7 +101,7 @@
+     }
+ 
+     @Override
+-    public void push(double deltaX, double deltaY, double deltaZ) {}
++    public void push(double deltaX, double deltaY, double deltaZ, @Nullable Entity pushingEntity) {} // Paper - Add EntityKnockbackByEntityEvent and EntityPushedByEntityAttackEvent
+ 
+     public abstract void explode(Vec3 pos);
+ 
 @@ -111,7 +114,7 @@
              Vec3 vec3d1 = blockHitResult.getLocation().add(vec3d);