fix: replace fs-extra.ensureFileSync with fs.writeFileSync

[erisu]

Motivation and Context

Fix undefined ensureFileSync method.

Description

The fs-extra npm package was removed which caused ensureFileSync to be not a function.

This PR replaces ensureFileSync with writeFileSync. The signing properties file is always removed before being recreated, and the platform directory should always exist, so it should be safe to call writeFileSync.

Testing

• npm t
• created a testing debug keystore file
• configured build.json to use the testing debug keystore.
• cordova build android
• cordova run android

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 71.89%. Comparing base (839f9b8) to head (b8e1d8f).

Files with missing lines	Patch %	Lines
lib/builders/ProjectBuilder.js	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1790   +/-   ##
=======================================
  Coverage   71.89%   71.89%           
=======================================
  Files          23       23           
  Lines        1854     1854           
=======================================
  Hits         1333     1333           
  Misses        521      521           

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[dpogue]

This looks fine to me.

With regards to the filesystem race condition, since we always overwrite the file if opts.packageInfo is set, is it fine to move the deletion to an else block and do it with { force: true } so we don't need to check existence?

[breautek]

lgtm