fix: multiple object updates of nested keys overwrite each other

[mstniy]

New Pull Request Checklist

• [x] I am not disclosing a vulnerability.
• [x] I am creating this PR in reference to an issue.

Issue Description

See #1450

Related issue: #1450

Approach

estimateAttributes only does deep copies when needed. It used to overwrite changes made to the same top-level field.

TODOs before merging

• [x] Add tests
• [ ] Add entry to changelog
• [ ] Add changes to documentation (guides, repository pages, in-code descriptions)

[parse-github-assistant[bot]]

Thanks for opening this pull request!

• 🎉 We are excited about your hands-on contribution!

[parse-github-assistant[bot]]

I will reformat the title to use the proper commit message syntax.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (72bc9ac) to head (60bf30e). Report is 15 commits behind head on alpha.

Additional details and impacted files

@@             Coverage Diff             @@
##            alpha     #1451      +/-   ##
===========================================
+ Coverage   99.98%   100.00%   +0.01%     
===========================================
  Files          61        64       +3     
  Lines        6185      6208      +23     
  Branches     1499      1503       +4     
===========================================
+ Hits         6184      6208      +24     
+ Misses          1         0       -1     

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[parseplatformorg]

🎉 This change has been released in version 5.1.0-alpha.7

[parseplatformorg]

🎉 This change has been released in version 5.1.0-beta.1

[parseplatformorg]

🎉 This change has been released in version 5.1.0