Fix server event race condition

[UkoeHB]

Closes #333

Solution:

• Buffer pre-serialized server events until a tick when ServerTick changes.
• Server events are optimistically pre-serialized with the latest server tick where an init message was sent. Then if client init ticks differ, they are reserialized with the correct tick.
• Server events are filtered against clients that connected after an event was sent to ensure connection boundaries are respected.

TODO:

• Add a test.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.09009% with 11 lines in your changes missing coverage. Please review.

Project coverage is 90.05%. Comparing base (0a61d5e) to head (f99ab54). Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/core/event_registry/server_event.rs	87.50%	10 Missing :warning:
src/server.rs	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #334 +/- ## ========================================== + Coverage 89.70% 90.05% +0.34% ========================================== Files 37 37 Lines 2322 2362 +40 ========================================== + Hits 2083 2127 +44 + Misses 239 235 -4 ```

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