FIR IDE: move low level api testdata sources to the analysis directory

analysis/low-level-api-fir/testdata/diagnosticTraversalCounter/nestedClases.kt

@@ -0,0 +1,11 @@
+class A {
+    class B {
+
+    }
+
+    object C {
+        class D {
+
+        }
+    }
+}