doc: Clarify JsonHandler semantics on EngineData ordering

[OussamaSaoudi]

What changes are proposed in this pull request?

When reading multiple log files during log replay, it is important that we read commits in order. This ensures the correctness of add/remove deduplication. Hence, we are implicitly relying on the commit files being read in order by the json handler.

Moreover when in-commit timestamps is enabled, the ordering of batches of engine data in a commit is important. A correct delta table should have the commit info be the first action in a log file.

This PR makes the expected semantics of the JsonHandler clearer with some added documentation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.43%. Comparing base (b3546f0) to head (961f039).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #635      +/-   ##
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- Coverage   83.45%   83.43%   -0.03%     
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  Files          75       75              
  Lines       16918    16918              
  Branches    16918    16918              
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- Hits        14119    14115       -4     
- Misses       2145     2147       +2     
- Partials      654      656       +2     

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[scovich]

Nice catch