Verify sequence when processing pushpull

[humdrum]

What this PR does / why we need it:

• Add sequence validation logic.
  • When applying changePack, the clientSeq sent by the server has to
    • '>=' the sequence of localChanges.first
    • '<=' the sequence of localChanges.last
    • If not, the client can't make a proper change pack.
  • When applying changePack, the serverSeq sent by the server has to equal to prevServerSeq + 1
• Update serverSeq with the actual data.
• Add Yorkie.sequenceCorrupted Error
  • Pause realtime sync when occurred.
• Add DocEvent corrupted.
  • When a document has a bad sequence. DocEvent.corrupted event fired.
  • Any suggestion for this is welcome. (@chacha912 )

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:
CI test will be success after yorkie-team/yorkie#503 is merged.

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

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

[codecov]

Codecov Report

Merging #66 (7e21e98) into main (b5ec0be) will decrease coverage by 0.21%.
The diff coverage is 7.04%.

@@            Coverage Diff             @@
##             main      #66      +/-   ##
==========================================
- Coverage   56.93%   56.72%   -0.21%     
==========================================
  Files          92       92              
  Lines       13953    14007      +54     
==========================================
+ Hits         7944     7946       +2     
- Misses       6009     6061      +52     

Impacted Files	Coverage Δ
Sources/Core/Client.swift	0.68% <0.00%> (-0.01%)	⬇️
Sources/Document/DocEvent.swift	0.00% <0.00%> (ø)
Sources/Document/Document.swift	32.75% <0.00%> (-7.79%)	⬇️
Sources/Document/Change/ChangeID.swift	93.02% <50.00%> (-6.98%)	⬇️
Sources/API/Converter.swift	60.39% <100.00%> (+0.05%)	⬆️

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[humdrum]

Since the sequence validation has been defined by the role of the server, this PR is closed.