add instrumented test

[skhugh]

What this PR does / why we need it?

Any background context you want to provide?

added instrumentet test to verify it is properly synced when multiple clients work on same document.

What are the relevant tickets?

Fixes #

Checklist

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

[codecov]

Codecov Report

Merging #44 (59f7df9) into main (2cb827e) will increase coverage by 1.39%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main      #44      +/-   ##
============================================
+ Coverage     77.61%   79.00%   +1.39%     
============================================
  Files            44       44              
  Lines          1724     1724              
  Branches        250      250              
============================================
+ Hits           1338     1362      +24     
+ Misses          250      223      -27     
- Partials        136      139       +3     

Impacted Files	Coverage Δ
yorkie/src/main/kotlin/dev/yorkie/core/Client.kt	84.81% <100.00%> (+4.89%)	⬆️
...ie/src/main/kotlin/dev/yorkie/document/Document.kt	87.87% <100.00%> (+1.28%)	⬆️
...c/main/kotlin/dev/yorkie/document/crdt/CrdtRoot.kt	65.85% <0.00%> (+7.31%)	⬆️
...main/kotlin/dev/yorkie/document/change/ChangeID.kt	90.90% <0.00%> (+9.09%)	⬆️
...in/kotlin/dev/yorkie/document/change/CheckPoint.kt	100.00% <0.00%> (+33.33%)	⬆️

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[hackerwins]

Thanks for your contribution. 👍