Add fix_drop_chance_bug configuration option.
This setting (default false) enables special handling of mob drops with near-unity (> 0.999) drop chance; on mob death, they are taken from the mob inventory and added to the drops collection, bypassing vanilla/Spigot/PaperSpigot drop code which has been buggy in the past. See: https://hub.spigotmc.org/jira/browse/SPIGOT-5298.
Unfortunately, in fixing a bug in skull comparison (https://hub.spigotmc.org/jira/browse/SPIGOT-5403:
ItemStack.isSimilar() returned true for different skulls), Spigot managed to introduce the opposite bug: isSimilar() returning false for identical skulls. That breaks this drop chance bug fix. That new Spigot bug persisted for a few days after Dec 6, 2019, before it was fixed by the Spigot project. During that small window, the PaperSpigot project pulled the buggy Spigot code and consequently ItemStack.isSimilar() is wrong for skulls in PaperSpigot builds 234 through 243. PaperSpigot has ceased development of 1.14.4 builds, meaning that the last ten PaperSpigot builds for 1.14.4 are not useable with this option enabled.