feat: add kotlin support

[erisu]

Motivation and Context

To finish off the change requests and close out PR #441

closes: #441

Description

What this PR does:

• Cherry-picks commit changes from CB-14089: (android) Add Kotlin support #441
• Rename preference option EnableKotlin to GradlePluginKotlinEnabled (Default: false)
  • Since the preference has not been released or used in any other repos, the name change is safe. This change is only an update from the original PR's proposal.
• Added preference options GradlePluginKotlinCodeStyle (Default: official)
• Added preference option GradlePluginKotlinVersion (Default: 1.3.50)
• Apply kotlin-android-extensions plugin as well when GradlePluginKotlinEnabled is true
• Changed compile to implementation

Testing

• npm t

Checklist

• I've run the tests to see all new and existing tests pass
• 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 (Pending Work for Cordova Docs Repo)

[codecov-io]

Codecov Report

Merging #896 into master will decrease coverage by 0.14%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #896      +/-   ##
==========================================
- Coverage   66.41%   66.27%   -0.15%     
==========================================
  Files          19       19              
  Lines        1849     1853       +4     
==========================================
  Hits         1228     1228              
- Misses        621      625       +4

Impacted Files	Coverage Δ
bin/templates/cordova/lib/prepare.js	34.65% <0%> (-0.47%)	⬇️

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[erisu]

@timbru31

I went ahead and created a new Kotlin support PR so we can quickly apply all the changes and improvements to get Kotlin prepared and released hopefully in the next day or 2.

Per your change request in the previous PR, I have:

• Updated Kotlin to the latest version

• Replaced mavenCentral with jcenter in the test/app/build.gradle

NOTICE:
This change is not applied to the actual build.gradle that is used when building a Cordova project. The actual file, bin/templates/project/app/build.gradle, still uses in the following order:

mavenCentral -> google -> jcenter

If these are to be updated, it should be taken care of in a separate PR

• Per your comment about kotlin:kotlin-stdlib-jdk7 I believe it is best to keep it as kotlin:kotlin-stdlib-jdk7. A newly created Android project with the official Android Studio uses kotlin:kotlin-stdlib-jdk7. Probably best to not do something different.

[erisu]

@timbru31 I just added the Kotlin source set as well, per your change request's overview comment. The only thing I was not sure is if it was necessary to wrap that behind a flag too.

[dpogue]

@timbru31 I just added the Kotlin source set as well, per your change request's overview comment. The only thing I was not sure is if it was necessary to wrap that behind a flag too.

IMO no need for a flag for adding the src/main/kotlin folder. Note that currently all plugin source files will end up in src/main/java because there's no special handling to detect kotlin files.

[timbru31]

is this the Android Studio default?

[erisu]

Yes, if you create a blank "No Activity" project in Android Studio, it has in the project's build.gradle:

ext.kotlin_version = '1.3.50'

[knight9999]

It looks fine.
I can run Kotlin code successfully with this PR.