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/writeSignature/DeepGenericInnerClass.kt

@@ -0,0 +1,15 @@
+abstract class Outer {
+    inner class FirstInner {
+        inner class SecondInner<A> {
+            inner class ThirdInnner {
+                inner class FourthInner<B>
+            }
+        }
+    }
+
+    fun <T, V> foo(): FirstInner.SecondInner<T>.ThirdInnner.FourthInner<V> = TODO()
+}
+
+// method: Outer::foo
+// jvm signature: ()LOuter$FirstInner$SecondInner$ThirdInnner$FourthInner;
+// generic signature: <T:Ljava/lang/Object;V:Ljava/lang/Object;>()LOuter$FirstInner$SecondInner<TT;>.ThirdInnner.FourthInner<TV;>;