ServerCore 1.16.5 - Zythera Safe Port

This is a clean-room Forge 1.16.5 implementation of the Entity Activation Range idea.
ServerCore by Wesley1808 was studied for feature behavior and configuration concepts.
ServerCore's upstream repository states that files explicitly marked GPL-3.0 are GPL-3.0
and the remaining files are MIT. This JAR intentionally does not copy or translate
GPL-marked ServerCore optimization source files.

The implementation uses Forge 1.16.5 Entity#canUpdate and Forge tick events and is not
full ServerCore 1.20.1 feature parity.
