Removed Lua callbacks from `MonsterType` of various monsters. These
callbacks were empty, which meant the functions were still being
"called" by the monsters without performing any action, creating a
significant performance bottleneck.
Removed the `onHear` event callback, which had a significant impact on
the server and was not used anywhere. It executed the `onHear` callback
for each spectator, causing an unnecessary overload without any real
benefit, especially as we have other methods to check for these events.
Additionally, the `monsterOnSpawn` event callback was removed and
replaced with `MonsterType::onSpawn`, which is much more efficient since
it only needs to be declared in the script for each monster that
actually uses it.
Finally, the way `setRewardBoss` was handled was improved. Previously,
it was executed in an `onSpawn` event callback, but now it is done
directly during the parsing of each monster script, marking them as
reward bosses at the time of script loading, improving efficiency.
