datatables cs2: update equipment owner

[micvbang]

This relates to #472.
This PR sets an equipment's owner to nil in cases where the equipment is destroyed or dropped, making GameState().Weapons() give a slightly more correct view of a player's weapons.

Note: in my experience it still shows duplicate knives and starter pistols.

EDIT: I wonder if the duplicate starter weapons are due to player deaths? 🤔

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f88e6d5) 80.50% compared to head (a4106dc) 80.40%.
Report is 1 commits behind head on master.

❗ Current head a4106dc differs from pull request most recent head e3feeed. Consider uploading reports for the commit e3feeed to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #473      +/-   ##
==========================================
- Coverage   80.50%   80.40%   -0.11%     
==========================================
  Files          47       47              
  Lines        6290     6281       -9     
==========================================
- Hits         5064     5050      -14     
- Misses       1017     1020       +3     
- Partials      209      211       +2     

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