Several fixes for Steam achievements / difficulty of the last boss — The PenguinGame 2 -Lies of Penguin- Steam update #346585

Made several fixes for Steam achievements intermittently not being awarded in situations where they should be earned. 1. Check if the achievement has been achieved and retry the achievement if necessary. 2. When the game is saved or loaded, check if all the achievements that should have been achieved have been achieved. The difficulty of the last boss fight has been slightly lowered.