Fix toJSON to always provide copy of data (cloneDeep)

[jusguy]

Pull Request check-list

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Description of change

Changes mode.toJSON() to always return a copy of the underlying data. This was a small change from lodash clone() to cloneDeep().

Closes #10052

[codecov]

Codecov Report

Merging #10058 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #10058   +/-   ##
=======================================
  Coverage    96.3%    96.3%           
=======================================
  Files          63       63           
  Lines        9410     9410           
=======================================
  Hits         9062     9062           
  Misses        348      348

Impacted Files	Coverage Δ
lib/model.js	96.67% <100%> (ø)	⬆️

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[sushantdhiman]

Thanks @justinkalland