[FIR] Add diagnostic collection to KotlinToJVMBytecodeCompiler

compiler/testData/cli/jvm/firError.kt

@@ -3,4 +3,10 @@ fun println(val x: Int) {}
 fun main() {
     val x: Int
     println(x)
+}
+
+private class Private
+
+class Public : Private() {
+    val x: Private
 }