Add RealtimeSyncOff and refactor interface of SyncMode

[humdrum]

What this PR does / why we need it:

• Add RealtimeSyncOff and refactor interface of SyncMode yorkie-js-sdk#772
• Remove redundant parameters of Client()

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

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

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 506 lines in your changes are missing coverage. Please review.

Project coverage is 41.12%. Comparing base (cbde6a0) to head (b5a5fea).

Files	Patch %	Lines
Tests/Integration/ClientIntegrationTests.swift	0.00%	352 Missing ⚠️
Tests/Integration/PresenceTests.swift	0.00%	46 Missing ⚠️
Sources/Core/Client.swift	0.00%	40 Missing ⚠️
Tests/Integration/GCTests.swift	0.00%	26 Missing ⚠️
Sources/Core/Attachment.swift	0.00%	12 Missing ⚠️
Tests/Integration/DocumentIntegrationTests.swift	0.00%	12 Missing ⚠️
Tests/Integration/CounterIntegrationTests.swift	0.00%	8 Missing ⚠️
Tests/Integration/TreeIntegrationTests.swift	0.00%	6 Missing ⚠️
Tests/Integration/IntegrationHelper.swift	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #160      +/-   ##
==========================================
+ Coverage   40.77%   41.12%   +0.35%     
==========================================
  Files         104      104              
  Lines       17967    17810     -157     
==========================================
- Hits         7326     7325       -1     
+ Misses      10641    10485     -156     

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