Lint Kotlin examples

[myyk]

• Needs Lint java examples #3919 as this builds on it

Last change I think needed for #3829

Overview:

• Changes KtfmtModule to set the error code when there's changes like is true of the other formatters.
• Some simplifications were made to the example/package.mill based on similarities with Java/Kotlin.
• Files were formatted
• CI was updated
  [ ] Not sure if KtfmtModule tests need updating as they aren't running cleanly from main on my machine.