Align generic signature for inner classes to work as in Java

#KT-10397 Fixed

According to JVMS (p. 4.3.4) inner classes should be separated with `$` in generic signature.

Note that in Java, inner types separated with `.` after first parameterized type, and now we preserve the same behaviour. See tests for clarification.

compiler/testData/codegen/box/reflection/genericSignature/signatureOfDeepGenericInner.kt

@@ -0,0 +1,23 @@
+// WITH_REFLECT
+// IGNORE_BACKEND: JS, NATIVE
+
+abstract class Outer {
+
+    inner class FirstInner {
+        inner class SecondInner<A> {
+            inner class ThirdInnner {
+                inner class FourthInner<B>
+
+                fun <C> foo(): FourthInner<C> = TODO()
+            }
+        }
+    }
+}
+
+fun box(): String {
+    kotlin.test.assertEquals(
+            "Outer\$FirstInner.Outer\$FirstInner\$SecondInner<A>.ThirdInnner.FourthInner<C>",
+            Outer.FirstInner.SecondInner.ThirdInnner::class.java.declaredMethods.single().genericReturnType.toString())
+
+    return "OK"
+}