Enable using Kotlin in Ion Java

[popematt]

Issue #, if available:

Description of changes:

Changes, grouped by commit:

• Update build to use Kotlin
  • There's a bunch of build logic that got added, but the key takeaway is that there's now a 3-stage jar process—compile, bundle & shadow, and finally minify
  • The r8 config rules are not obfuscating as a way of minifying, so stack traces are not affected.
  • Adds Gradle task to generate third-party attribution file for the published jar
  • Adds THIRD_PARTY_LICENSES.md file for the GitHub repo
  • Adds Gradle task to make sure that the THIRD_PARTY_LICENSES.md file is up-to-date with the actual state of reality.
• Rewrite a class in Kotlin
  • This is mostly just to prove that the whole thing works
• Fix ktlint violations
  • ktlint is an anti-bikeshedding linter for Kotlin. It's pretty opinionated about unused imports, and apparently it can detect them even in a Java file.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[popematt]

Marking as "ready for review" so that it will run all of the workflows. Not actually ready for review yet.

[codecov]

Codecov Report

Attention: 17 lines in your changes are missing coverage. Please review.

Comparison is base (b08cbc4) 67.05% compared to head (2a193e7) 67.01%.

Files	Patch %	Lines
src/com/amazon/ion/impl/IonIteratorImpl.kt	56.41%	13 Missing and 4 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #488      +/-   ##
============================================
- Coverage     67.05%   67.01%   -0.05%     
+ Complexity     5462     5459       -3     
============================================
  Files           159      159              
  Lines         22987    22938      -49     
  Branches       4117     4113       -4     
============================================
- Hits          15415    15371      -44     
+ Misses         6295     6291       -4     
+ Partials       1277     1276       -1     

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[tgregg]

What's the purpose of this?

[popematt]

If e.g. Java 17 task fails, it won't cancel the Java 11 task. I added it earlier on when we were still using JDK 8 and JDK 11, and there legitimately were reasons why it might fail for one and succeed for the other. I don't know if that's still possible between JDK 11 and JDK 17, but these tasks are relative short (matter of minutes) so if the task is already running why bother cancelling it? Just let it run.