fix broken portal spawn and dragon skip

EnderDragonFightMixin.java

import com.llamalad7.mixinextras.injector.ModifyExpressionValue;
import net.minecraft.entity.boss.dragon.EnderDragonFight;
import net.minecraft.util.math.BlockPos;
import org.objectweb.asm.Opcodes;
import org.spongepowered.asm.mixin.*;
import org.spongepowered.asm.mixin.injection.At;

@Mixin(EnderDragonFight.class)
public abstract class EnderDragonFightMixin {
    @Shadow
    private boolean doLegacyCheck;

    @ModifyExpressionValue(method = "generateEndPortal", at = @At(value = "INVOKE", target = "Lnet/minecraft/util/math/BlockPos;down()Lnet/minecraft/util/math/BlockPos;", ordinal = 0))
    private BlockPos appropriateMin(BlockPos original) {
        return new BlockPos(original.getX(), Math.max(original.getY(), 1), original.getZ());
    }

    @ModifyExpressionValue(method = "respawnDragon()V", at = @At(value = "FIELD", target = "Lnet/minecraft/entity/boss/dragon/EnderDragonFight;dragonKilled:Z", opcode = Opcodes.GETFIELD))
    private boolean respawnCheckIfDoingLegacyCheck(boolean original) {
        return original && !this.doLegacyCheck;
    }
}