Add multiplatform test with substitution, fix deep supertypes

This commit fixes ambiguity problems introduced before
in MPP tests with deep supertypes

#KT-29636 Fixed

idea/testData/fir/multiModule/mppFakeOverrides/common/common.kt

@@ -0,0 +1,10 @@
+expect open class A<T>() {
+    open fun foo(arg: T)
+}
+open class B : A<String>() {
+    // Fake: override fun foo(arg: String) = super.foo(arg)
+    // Fake (JVM only) (?): override fun bar(arg: String): String = super.bar(arg)
+}
+open class C : B() {
+    open fun bar(arg: CharSequence): String = arg.toString()
+}

idea/testData/fir/multiModule/mppFakeOverrides/common/common.txt

@@ -0,0 +1,19 @@
+FILE: common.kt
+    <T> public open expect class A {
+        public constructor(): super<R|kotlin/Any|>()
+
+        public open function foo(arg: R|T|): R|kotlin/Unit|
+
+    }
+    public open class B : R|A<kotlin/String>| {
+        public constructor(): super<R|A<kotlin/String>|>()
+
+    }
+    public open class C : R|B| {
+        public constructor(): super<R|B|>()
+
+        public open function bar(arg: R|kotlin/CharSequence|): R|kotlin/String| {
+            return@@@bar <Unresolved name: arg>#.<Unresolved name: toString>#()
+        }
+
+    }

idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.kt

@@ -0,0 +1,11 @@
+actual open class A<T> {
+    actual open fun foo(arg: T) {}
+    open fun bar(arg: T): T = arg
+}
+class D : C() {
+    // Fake: override fun bar(arg: CharSequence): String = super.bar(arg)
+    fun test() {
+        foo("")
+        bar("")
+    }
+}

idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.txt

@@ -0,0 +1,21 @@
+FILE: jvm.kt
+    <T> public open actual class A {
+        public constructor(): super<R|kotlin/Any|>()
+
+        public open actual function foo(arg: R|T|): R|kotlin/Unit| {
+        }
+
+        public open function bar(arg: R|T|): R|T| {
+            return@@@bar <Unresolved name: arg>#
+        }
+
+    }
+    public final class D : R|C| {
+        public constructor(): super<R|C|>()
+
+        public final function test(): R|kotlin/Unit| {
+            R|FakeOverride</A.foo>|(String())
+            R|FakeOverride</A.bar>|(String())
+        }
+
+    }

idea/testData/fir/multiModule/mppMembers/jvm/jvm.txt

@@ -13,8 +13,8 @@ FILE: jvm.kt
         public constructor(): super<R|B|>()
 
         public final function test(): R|kotlin/Unit| {
-            <Ambiguity: foo, [/A.foo, /A.foo]>#()
-            <Ambiguity: bar, [/A.bar, /A.bar]>#()
+            R|/A.foo|()
+            R|/A.bar|()
         }
 
     }

idea/testData/fir/multiModule/mppSuperTypes/jvm/jvm.txt

@@ -22,7 +22,7 @@ FILE: jvm.kt
         public constructor(): super<R|B|>()
 
         public final function test(): R|kotlin/Unit| {
-            <Ambiguity: foo, [/A.foo, /A.foo]>#()
+            R|/A.foo|()
             <Unresolved name: bar>#()
             <Unresolved name: baz>#()
         }
@@ -33,8 +33,8 @@ FILE: jvm.kt
 
         public final function test(): R|kotlin/Unit| {
             R|/A.foo|()
-            <Ambiguity: bar, [/X.bar, /X.bar]>#()
-            <Ambiguity: baz, [/Y.baz, /Y.baz]>#()
+            R|/X.bar|()
+            R|/Y.baz|()
         }
 
     }