Make runWatchLoop to react to attachments changes

[skhugh]

What this PR does / why we need it?

Makes runWatchLoop to react to attachments changes.
This makes watch loop to keep running while the client is active which makes it similar to how runSyncLoop runs.
Also it removes multiple explicit call-sites of runWatchLoop everytime attachments change, which was error-prone.

Any background context you want to provide?

What are the relevant tickets?

Fixes #

Checklist

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

[codecov]

Codecov Report

Merging #77 (ab14eb2) into main (c194956) will increase coverage by 0.17%.
The diff coverage is 82.14%.

@@            Coverage Diff             @@
##             main      #77      +/-   ##
==========================================
+ Coverage   80.97%   81.14%   +0.17%     
==========================================
  Files          52       52              
  Lines        2370     2371       +1     
  Branches      337      336       -1     
==========================================
+ Hits         1919     1924       +5     
+ Misses        260      258       -2     
+ Partials      191      189       -2     

Impacted Files	Coverage Δ
...in/kotlin/dev/yorkie/document/crdt/RgaTreeSplit.kt	65.53% <80.00%> (ø)
yorkie/src/main/kotlin/dev/yorkie/core/Client.kt	86.44% <80.43%> (+1.63%)	⬆️
...rkie/src/main/kotlin/dev/yorkie/core/Attachment.kt	100.00% <100.00%> (ø)
...main/kotlin/dev/yorkie/document/crdt/CrdtObject.kt	90.69% <100.00%> (ø)

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[hackerwins]

Thanks for your contribution.