Reset online clients when stream is disconnected

[chacha912]

What this PR does / why we need it?

When the stream is disconnected, online-clients' information should be cleared and no longer accessible.

reset-unwatch.mov

Any background context you want to provide?

Before, the initialized event only occurred when first attaching to the document, indicating who was using it. Now, it also occurs if the watch stream is disconnected and clients have reset.

What are the relevant tickets?

Address #791

Checklist

• Added relevant tests or not required
• Didn't break anything

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.50%. Comparing base (cd33ea7) to head (5586540).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #796      +/-   ##
==========================================
+ Coverage   80.24%   80.50%   +0.26%     
==========================================
  Files          59       59              
  Lines        4439     4448       +9     
  Branches      898      901       +3     
==========================================
+ Hits         3562     3581      +19     
+ Misses        613      605       -8     
+ Partials      264      262       -2     

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[hackerwins]

Thanks for your contribution.