Add test methods and data for uncommon cases

Uncommon means mostly that aren't present in raw fir builder data

compiler/visualizer/testData/uncommonCases/resultFiles/variance.kt

@@ -0,0 +1,24 @@
+interface Source<out T> {
+    fun nextT(): T
+}
+
+fun demo(strs: Source<String>) {
+//      Source<Any>            demo.strs: Source<String>
+//      │                      │
+    val objects: Source<Any> = strs
+}
+
+interface Comparable<in T> {
+    operator fun compareTo(other: T): Int
+}
+
+fun demo(x: Comparable<Number>) {
+//  demo.x: Comparable<Number>
+//  │ fun (Comparable<Number>).compareTo(Number): Int
+//  │ │         Double
+//  │ │         │
+    x.compareTo(1.0)
+//      Comparable<Double>      demo.x: Comparable<Number>
+//      │                       │
+    val y: Comparable<Double> = x
+}