breaking: add & use fs-extra w/ fixes

[erisu]

Motivation, Context & Description

• Add fs-extra dependency
• Replace fs usage with fs-extra
• Replace test spec xml generating logic and use pre-made xml test fixtures. Lower the amount of call mocks with actual tool usage for improved testing.

Testing

• npm t

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change

[codecov-commenter]

Codecov Report

Merging #847 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #847   +/-   ##
=======================================
  Coverage   74.40%   74.40%           
=======================================
  Files          13       13           
  Lines        1821     1821           
=======================================
  Hits         1355     1355           
  Misses        466      466           

Impacted Files	Coverage Δ
bin/templates/scripts/cordova/Api.js	71.42% <100.00%> (ø)
...in/templates/scripts/cordova/lib/BridgingHeader.js	95.45% <100.00%> (ø)
bin/templates/scripts/cordova/lib/Podfile.js	73.58% <100.00%> (ø)
bin/templates/scripts/cordova/lib/PodsJson.js	95.04% <100.00%> (ø)
bin/templates/scripts/cordova/lib/build.js	50.76% <100.00%> (ø)
...ates/scripts/cordova/lib/plugman/pluginHandlers.js	90.20% <100.00%> (ø)
bin/templates/scripts/cordova/lib/prepare.js	82.05% <100.00%> (ø)
bin/templates/scripts/cordova/lib/projectFile.js	94.64% <100.00%> (ø)

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[timbru31]

Replace test spec xml generating logic and use pre-made xml test fixtures. Lower the amount of call mocks with actual tool usage for improved testing.

Very nice!