Basic version of CONFLICTING_PLATFORM_DECLARATIONS diagnostic
Repoting platform declarations clashes in CLI compiler for JVM
Cache KotlinLightClassForPackage instances per project
Report clashing signatures in the IDE

Expose extra diagnostics about platform signature clashes from light class data
Diagnostic tests for duplicate JVM signatures
++ Tests for traits
++ Tests for extensions
++ Tests for properties
++ Tests for erasure
++ Tests for accidental overrides
++ ++ Tests for erasure
++ Tests for special names
++ Tests for erasure
JvmDeclarationOrigin used in newField()
JvmDeclarationOrigin used in newMethod()
JvmDeclarationOrigin used in newVisitor()
JvmDeclarationOrigin used in newClassBuilder()
Package part and facade origins supported
TraitImpl origin supported
JvmDeclarationOrigin used in FunctionCodegen.generateMethod()