Investigate FIR for better IDE integration

[swankjesse]

I asked my Kotlin Multiplatform testing expert friend @bnorm about IDE integration and he suggested this:

I wonder if an FIR plugin might help with the back navigation from the run dashboard? Ultimately the IDE is looking for a PSI element with the right class/method name and if you generate it in FIR you might be able to back navigate to the source of the generation.

He suggested some sample projects to look at:

https://github.com/JetBrains/kotlin/tree/master/plugins/plugin-sandbox
https://github.com/demiurg906/kotlin-compiler-plugin-template
https://github.com/bnorm/piecemeal

[JakeWharton]

FIR will also mean the ability to report problems with the signatures in the IDE, such as the use of unsupported types.