breaking: replace shelljs with fs-extra

[erisu]

Motivation, Context & Description

• Remove shelljs dependency for fs-extra.

Testing

• npm t

Checklist

• I've run the tests to see all new and existing tests pass

[codecov-commenter]

Codecov Report

❌ Patch coverage is 76.19048% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.76%. Comparing base (67bea75) to head (b9b99fa).
⚠️ Report is 291 commits behind head on master.

Files with missing lines	Patch %	Lines
bin/templates/scripts/cordova/lib/build.js	50.00%	2 Missing ⚠️
bin/templates/scripts/cordova/lib/run.js	0.00%	2 Missing ⚠️
...ates/scripts/cordova/lib/plugman/pluginHandlers.js	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #851      +/-   ##
==========================================
- Coverage   74.85%   74.76%   -0.09%     
==========================================
  Files          13       13              
  Lines        1742     1736       -6     
==========================================
- Hits         1304     1298       -6     
  Misses        438      438              

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[breautek]

LGTM