Migrate to Kotlin 2.1

[barbulescu]

What's changed?

What's your motivation?

Anything in particular you'd like reviewers to focus on?

Anyone you would like to review specifically?

Have you considered any alternatives or workarounds?

Any additional context

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[github-actions]

Some suggestions could not be made:

• src/test/java/org/openrewrite/kotlin/ChangeTypeTest.java
  • lines 18-18

[github-actions]

Suggested change

	private fun Any?.isInvalid() = this == null
	|| this is FirErrorTypeRef
	|| this is FirExpression && this.resolvedType is ConeErrorType
	|| this is FirResolvedQualifier && classId == null
	private fun Any?.isInvalid() = this == null ||
	this is FirErrorTypeRef ||
	this is FirExpression && this.resolvedType is ConeErrorType ||
	this is FirResolvedQualifier && classId == null

[timtebeek]

Adding a quick note here that we've since moved this repository into openrewrite/rewrite; let us know if you'd like help porting over the work you have done here!