Add changelog snippet for #6134 (#6183)

Co-authored-by: lL1l1 <82986251+lL1l1@users.noreply.github.com>

changelog/snippets/other.6134.md

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+- (#6134) Various general fixes and optimizations for the Cooperative AI, along with a change to its base building logic from a thread-based one to using unit callbacks, resulting in more reliable structure registrations and upgrades.